Investigators are looking into possible links between Tamerlan Tsarnaev, 26, and a Canadian boxer-turned-jihadist killed in a firefight with Russian forces in the southwestern republic of Dagestan in July 2012, while Tsarnaev was visiting the region, CNN reported citing sources.

Tamerlan Tsarnaev flew out of Dagestan two days after the burial of William Plotnikov, 23, who had been born in Russia, but his family moved to Canada when he was a teenager, the channel said. Investigators are looking into the possibility he left because of Plotnikov's death, CNN said citing sources.