FBI searches home of Tamerlan Tsarnaev's in-laws

FBI agents investigating the Boston Marathon bombings have visited the Rhode Island home of Tamerlan Tsarnaev's in-laws and carried away several bags.

A spokesman confirms that agents went to the North Kingstown, R.I., home of Katherine Russell Tsarnaeva's parents Monday. After agents left the home, Russell left with her attorneys through a separate door. The lawyers didn't immediately return messages.

• Boston investigators attempt to pin down Tsarnaev brothers' influences
• Chambliss: Boston bombers "our worst fear"
• Did a brotherly bond influence the Boston bombing suspects?
• Boston bombing victim: I'm one of the lucky ones

Katherine Tsarnaeva, Tsarnaev's widow, has been staying there. CBS News correspondent Bob Orr reports the FBI went the home to collect a DNA sample.

Sources tell Orr female DNA has been found on a fragment of one of the bombs used in the attack. The DNA could have come from a spectator in the crowd or a clerk who sold the bomb-making materials, but investigators say it's also possible it could have come from a female accomplice.

Tsarnaeva's lawyer said she was clueless about her husband's plans and the news "came as an absolute shock to them all." Since the Tsarnaevs were identified by the FBI as suspects, Tsarnaeva has not talked publicly.

"[She is] doing everything she can" to assist authorities and is "trying to come to terms with these events," lawyer Amato DeLuca said last week.

Tsarnaeva dropped out of college in Boston and converted to Islam before marrying her husband in 2010. They have a little girl. She grew up with two younger sisters in a Christian family on a quiet cul-de-sac in North Kingstown, a rural, wooded town.

Her lawyer said she had no reason to suspect her husband of anything and was focused on supporting her family, working 70 to 80 hours, seven days a week as a home health care aide. Her husband cared for their daughter when she was away, DeLuca said.

Tamerlan Tsarnaev was killed in a gun battle with police about two weeks ago. Dzhokhar Tsarnaev has been charged with using a weapon of mass destruction.

Investigators are delving deeply into the lives of the two brothers for any clues as to what set them on a path toward terrorism. Authorities say there is no evidence suggesting the brothers were a part of a larger terrorist group, but they continue to probe potential outside influences.

Lawmakers are questioning whether the suspected bombers got help. Rep. Michael McCaul, a Texas Republican and chair of the House Committee on Homeland Security, said on Fox News Sunday that he thinks "the experts all agree that there is someone who did train these two individuals."

House Intelligence Committee chairman, Rep. Mike Rogers, R-Mich., also said the FBI wants to interview anyone who may have known about the Tsarnaevs' alleged plot. "We still have persons of interest that we're working to find and identify and have conversations with," Rogers said.

The Tsarnaevs' mother may hold the key to some answers. In 2011, Russian authoritiessecretly recorded a phone call between here and Tamerlan Tsarnaev in which the two vaguely discussed "jihad." The FBI says it only learned the details of that conversation days ago, even though Russian authorities asked them to look into Tamerlan in 2011.

Sunday on "Face the Nation," Sen. Lindsey Graham, R-S.C., said, "The warning letters the FBI received in March of 2011 and the CIA, I think in November 2011, included the mother as someone to be worried about."

CBS News senior correspondent John Miller, a former assistant FBI director, said on "CBS This Morning," "This is one of those cases where we're looking for the radicalizer, we're looking for the bomb maker, and as the case unfolds -- and I always say this can change -- we're coming into our third weekend of this. But they've got a long way to go. So far, it looks like these were the actions of Tamerlan Tsarnaev, maybe egged on by his mother, but there doesn't seem to be a giant organization behind it."

The suspects' mother, Zubeidat Tsarnaeva, has repeatedly denied that she or her sons had any involvement with terrorist organizations.

As for the suggestion by some in Congress that the Tsarnaev brothers had some sort of training, Miller said, "It suggests what members of Congress know about bomb making. If you look at the ... instruction page that gave them the layout for how to make the pressure cooker bomb, they're saying the remote control aspect is something that they would have had to go somewhere else, well, scroll down that page in the magazine and the very next picture after the pressure cooker is how to do the remote control. This can be done, and it can be done by dummies."

Nineteen-year-old Dzhokar remains at a federal medical detention center 40 miles from Boston. He's locked inside a 10-by-10-foot cell with a steel door and a slot for food.