Officials probe Boston bombing suspect's trip to Russia

Congressional intelligence leaders said Sunday that authorities are pursuing "persons of interest" in the United States in connection with the Boston Marathon bombings, and asked for more help from Russian spy agencies.

Rep. Mike Rogers (R-Mich.), chairman of the House Intelligence Committee, told ABC that the government is seeking out anyone inside the U.S. who may have been a part of the plot, as well as information about Tamerlan Tsarnaev's trip to Russia last year.

"There are still persons of interest in the United States that the FBI would like to have conversations with," Rogers said. "And the big unknown is still that six months, little over six months in Russia."

He added: "The Russians need to step up to the plate here and provide us better information. ? I think they have information that would be incredibly helpful that they haven't provided yet."

New details of the unfolding investigation emerged following reports on Saturday that Tamerlan Tsarnaev spoke to his mother about "jihad" in a 2011 phone call secretly recorded by Russian officials.

U.S. authorities learned of the wiretapped discussion between Tsarnaev and his mother, Zubeidat Tsarnaeva, within the last few days, CBS News reported. Tsarnaev died in an April 18 shootout with police, three days after the bombings that killed three people and injured 264.

The revelations that others are being sought for questioning came as the suspected bombers' father told Reuters Sunday that he has abandoned plans to travel to the U.S.