Photos of one of two suspects sought in the Boston Marathon bombing is displayed during a news conference talking about the investigation of the Boston Marathon explosions, Thursday, April 18, 2013, in Boston. The city continues to cope following Monday's explosions near the finish line of the marathon. (AP Photo/Julio Cortez)
WASHINGTON - - The chairman of the House Homeland Security Committee says the FBI is investigating both in the United States and overseas to determine whether the two suspects in the Boston Marathon bombing received training.
U.S. officials say there is no evidence to date of a wider plot.
But Rep. Michael McCaul tells "Fox News Sunday" the shrapnel-packed pressure cooker bombs used in the attacks leads him to believe that someone did train the bombers.
McCaul also says he thinks the mother of Tamerlan and Dzhokhar Tsarnaev played "a very strong role" in her sons' radicalization process.
Russian's internal security service is refusing comment on reports that it secretly recorded a telephone conversation in 2011 in which one of the Boston bombing suspects discussed jihad with his mother. But the U.S. government received details about the call a few days ago and officials describe the conversation as vague. They say Tamerlan Tsarnaev and his mother discussed the possibility of going to Palestine, but he told his mother he didn't speak the language.
Tamerlan Tsarnaev was killed in a shootout with police.