House Homeland Security Chairman Michael McCaul (R-Texas) said on Sunday that he believes the Boston bombers had sophisticated training.
"And the question is where is that trainer or trainers?" McCaul said on Fox News Sunday. "Are they overseas in the Chechen region or are they in the United States?"
He said the FBI has cast a "wide net" in the hunt for a possible trainer.
"I think the experts all agree that there is someone who did train these two individuals," McCaul said.
Brothers Tamerlan and Dzhokhar Tsarnaev are believed to have detonated two homemade bombs packed with shrapnel at the finish line of the Boston Marathon, killing three and maiming dozens.
Tamerlan Tsarnaev was killed after a shootout with police, but his younger brother has been charged in the attacks. Dzhokhar Tsarnaev has said he and his brother were radicalized on the internet and suggested they learned how to build the bombs from instructions in an al Qaeda magazine, according to reports.
Bit Sen. Joe Manchin (D-W.Va.) agreed with McCaul, saying the bombings were "more advanced" than what would have been possible with Internet research.
McCaul also said he believes the mother of the two suspected bombers played a "role in the radicalization process" and called her a "person of interest," but stopped short of claiming she was involved in the bombing.
Reports Saturday said that Russian officials may have recordings of the mother discussing "jihad' with one of her sons.