FROM CNN WIRES:

(CNN) - Federal agents are looking into possible links between dead Boston Marathon bomb suspect Tamerlan Tsarnaev and a Canadian boxer-turned-jihadist killed by Russian troops in 2012, a source being briefed on the investigation said Monday.

William Plotnikov and six others died in a firefight with Russian forces in the southwestern republic of Dagestan in July 2012, while Tsarnaev was visiting the region, the source said. The 23-year-old Plotnikov was born in Russia, but his family moved to Canada when he was a teenager.

The source said Plotnikov's body was prepared for burial by a local imam on July 14. Tsarnaev flew out of Dagestan two days later, arriving in New York on July 17. Investigators are looking into the possibility he left because of Plotnikov's death, the source said.

This morning on "Early Start," CNN's Phil Black reports on possible links between Tamerlan Tsarnaev and Canadian boxer-turned-jihadist William Plotnikov.

READ MORE: Boston probe eyes slain Canadian jihadist, source says