Nearly three weeks after the disappearance of Malaysia Airlines Flight 370, the focus of the hunt for the missing passenger jet has moved yet again.

Search teams have shifted to a different part of the southern Indian Ocean after Australian authorities said they received "a new credible lead" about the jetliner's most likely last movements.

An analysis of radar data led investigators to move the search to an area 1,100 kilometers (680 miles) to the northeast of where efforts had been focused previously, the Australian Maritime Safety Authority said Friday.

It described the new information, which indicated the errant jetliner didn't fly as far south as previously thought, as "the most credible lead to where debris may be located."

That means the huge, isolated areas of the ocean that ships and planes had combed for more than a week - and where various satellites detected objects that might be debris from the missing plane - are no longer of interest.

"We have moved on from those search areas," said John Young, general manager of emergency response for the Australian maritime authority.

The new search area is "considerable" and conditions there "remain challenging," acting Malaysian Transport Minister Hishammuddin Hussein told reporters Friday.

The sudden change of geographic focus is the latest twist in an investigation that has so far failed to establish why Flight 370 flew dramatically off course or exactly where the plane and the 239 people it was carrying ended up.

"To me, it's not a game changer, it's a reset," David Gallo of theWoods Hole Oceanographic Institution said of the shifted search.

'We have not seen any debris'

Australian officials also played down the significance of hundreds of possible objects detected by satellites in the previous search region, some of which had been described by authorities as important leads.

"In regards to the old areas, we have not seen any debris," Young said at a news briefing in Canberra, the Australian capital. "And I would not wish to classify any of the satellite imagery as debris, nor would I want to classify any of the few visual sightings that we made as debris. That's just not justifiable from what we have seen."

Officials had repeatedly cautioned that the objects seen in the satellite imagery could just be flotsam that had fallen off cargo ships.

But Hishammuddin said the new search area "could still be consistent" with the idea that materials spotted in recent satellite photos over the previous search area are connected to the plane. The materials could have drifted in ocean currents, he said.

Some analysts raised their eyebrows at the search coordinators' readiness to move away from the satellite sightings.

"Really? That much debris and we're not going to have a look at it to see what that stuff might be?" said Gallo, who helped lead the search for the flight recorders of Air France Flight 447, which crashed into the Atlantic Ocean in 2009.

Others lamented the amount of time, money and resources that were spent sending planes and ships out to the now discounted areas for more than a week.

"This is time that has been wasted, there's no question," said CNN aviation analyst Miles O'Brien.

But Young disputed that suggestion, saying the previous searches were based on the information authorities "had at the time."

"That's nothing unusual for search and rescue operations," he said "And this actually happens to us all the time - that new information may arise out of sequence with the search itself."

The crew of a Chinese plane searching for the missing Malaysia Airlines Flight 370 spotted "suspicious objects" in the southern Indian Ocean on Monday, the latest lead in a long and often frustrating investigation.

But a high-tech U.S. search aircraft that followed up on the sighting couldn't find them again, Australian authorities said.

A reporter on board the Chinese plane for China's official news agency Xinhua said the search team saw "two relatively big floating objects with many white smaller ones scattered within a radius of several kilometers," the agency reported.

The Australian Maritime Safety Authority said on Twitter that a U.S. Navy P8 Poseidon aircraft that was tasked to investigate the objects was unable to relocate them.

The IL-76 plane that reported the objects is one of two Chinese military aircraft helping scour a remote area of the southern Indian Ocean on Monday for traces of the passenger jet, which disappeared over Southeast Asia on March 8 with 239 people on board.

With the search in its third week, authorities have so far been unable to establish where exactly the plane is or why it flew off course from its planned journey from Kuala Lumpur to Beijing.

China has a particularly large stake in the search: its citizens made up about two thirds of the 227 passengers on the missing Boeing 777. Beijing has repeatedly called on Malaysian authorities, which are in charge of the overall search, to step up efforts to locate the plane.

A Chinese icebreaker in the region, the Xuelong, has changed course and is headed toward the area where the objects were seen by the Chinese plane, Xinhua said.

Satellites focus search

Recent information from satellites identifying objects in the water that could be related to the plane has focused the search efforts on an area roughly 1,500 miles southwest of the Australian city of Perth.

Eight other aircraft - from Australia, the United States and Japan - are also tasked with combing the search area over the course of Monday.

The two Chinese aircraft are now heading back to base, Xinhua reported. The crew that spotted the objects has asked Australia authorities to send other planes to the area of interest, it said.

The aerial searches have been trained on the isolated part of ocean since last week, when Australia first announced that satellite imagery had detected possible objects that could be connected to the search.

Since then, China and France have said they also have satellite information pointing to floating debris in a similar area. The Chinese information came from images, and the French data came from satellite radar.

But Australian officials have repeatedly warned that the objects detected in satellite images may not turn out to be from the missing plane - they could be containers that have fallen off cargo ships, for example.

The investigation into the passenger jet's disappearance has already produced a wealth of false leads and speculative theories. Previously, when the hunt was focused on the South China Sea near where the plane dropped off civilian radar, a number of sightings of debris proved to be unrelated to the search.

Plane said to have flown low

The sighting of the objects of interest by the Chinese plane came after a weekend during which other nuggets of information emerged about the movements of the errant jetliner on the night it vanished.

Military radar tracking shows that after making a sharp turn over the South China Sea, the plane changed altitude as it headed toward the Strait of Malacca, an official close to the investigation into the missing flight told CNN.

The plane flew as low as 12,000 feet at some point before it disappeared from radar, according to the official. It had reportedly been flying at a cruising altitude of 35,000 feet when contact was lost with air traffic control.

The sharp turn seemed to be intentional, the official said, because executing it would have taken the Boeing 777 two minutes - a time period during which the pilot or co-pilot could have sent an emergency signal if there had been a fire or other emergency onboard.

Authorities say the plane didn't send any emergency signals, though some analysts say it's still unclear whether the pilots tried but weren't able to communicate because of a catastrophic failure of the aircraft's systems.

The official, who is not authorized to speak to the media, told CNN that the area the plane flew in after the turn is a heavily trafficked air corridor and that flying at 12,000 feet would have kept the jet well out of the way of that traffic.

Malaysia disputes reprogramming

Also over the weekend, Malaysian authorities said the last transmission from the missing aircraft's reporting system showed it heading to Beijing - a revelation that appears to undercut the theory that someone reprogrammed the plane's flight path before the co-pilot signed off with air-traffic controllers for the last time.

That reduces, but doesn't rule out, suspicions about foul play in the cockpit.

The new details give more insight about what happened on the plane, but don't explain why the plane went missing or where it could be.

Analysts are divided about what the latest information could mean. Some argue it's a sign that mechanical failure sent the plane suddenly off course. Others say there are still too many unknowns to eliminate any possibilities.

CNN aviation analyst Miles O'Brien called the fresh details about the flight a "game changer."

"Now we have no evidence the crew did anything wrong," he said. "And in fact, now, we should be operating with the primary assumption being that something bad happened to that plane shortly after they said good night."

If a crisis on board caused the plane to lose pressure, he said, pilots could have chosen to deliberately fly lower to save passengers onboard.

"You want to get down to 10,000 feet, because that is when you don't have to worry about pressurization. You have enough air in the atmosphere naturally to keep everybody alive," he said. "So part of the procedure for a rapid decompression ... it's called a high dive, and you go as quickly as you can down that to that altitude."

Flight makes emergency landing

Adding to the negative publicity that has blighted Malaysia Airlines since news of Flight 370's disappearance, one of the carrier's passenger jets made an emergency landing in Hong Kong on Monday.

The plane, scheduled to fly from Kuala Lumpur to Incheon, South Korea, was diverted to Hong Kong after its main electrical generator stopped working. Electrical power continued to be supplied by the plane's auxiliary power unit, Malaysia Airlines said

The Airbus A330-300 landed safely at Hong Kong airport around 3 a.m., and the 271 passengers on board have been transferred onto flights with other airlines.