Zubeidat Tsarnaeva, the mother of the two Boston bombing suspects...

Zubeidat Tsarnaeva, the mother of the two Boston bombing suspects in Makhachkala, the southern Russian province of Dagestan. (April 25, 2013)

BOSTON -- The mother of the brothers suspected of bombing the Boston Marathon was on the same U.S. government terrorist watch list as the older son -- and investigators are probing whether she knew in advance about the plot, according to a federal law enforcement source.

The pair -- mother Zubeidat Tsarnaeva and the older son, Tamerlan Tsarnaev -- had been added to the list in 2011 after Russian state security asked U.S. counterparts to investigate him over fears he might return to Russia to join a militant group. Russian authorities were also worried about the mother, the source said.

That same year, the mother sent text messages to relatives saying that Tamerlan Tsarnaev, who was then living in Cambridge, Mass., with his brother, was willing to die for Islam -- messages that U.S. intelligence analysts uncovered, according to the source.

It was unclear whether those messages factored into the decision to add her to the list, nor was it clear when and how the intelligence analysts happened to uncover the messages.

The revelations about the family came as the younger accused bomber, Dzhokhar Tsarnaev, was transferred from a civilian hospital here, Beth Israel Deaconess Medical Center, to the Federal Medical Center Devens, a prison hospital about 40 miles west, according to the U.S. Marshals Service, which has responsibility for people awaiting trial.

Dzhokhar Tsarnaev, 19, was charged Monday with use of a weapon of mass destruction and malicious destruction of property resulting in death for the two bombings at the marathon.

At the medical center, which houses chronically ill inmates on what is a decommissioned military base, Tsarnaev will continue treatment for gunshot wounds sustained during a shootout with police days after the bombings.

Global investigation

Three people died and more than 260 were injured on April 15 when the brothers allegedly set off two shrapnel-laden pressure-cooker bombs, apparently using refashioned toy remote controls, near the finish line of the 117th Boston Marathon.

Three days later, the brothers assassinated a Massachusetts Institute of Technology police officer, carjacked a Mercedes driver, engaged in a bomb-throwing shootout with pursuing police and wounded a transit cop, officials said. The older brother died in the firefight but the younger one escaped, only to be found later that day hiding in a dry-docked boat near the gunfight scene.

An FBI analysis of the recovered explosives and explosive parts shows that whoever built the pressure cooker bombs and pipe bombs followed the instructions in al-Qaida's "Inspire" magazine "almost exactly," the source said.

The pressure cooker bombs used explosive powder from fireworks and spherical shrapnel probably held inside the bomb with glue -- all things recommended by the publication, the source said.

Investigators in the United States and in the family's home region of Dagestan, a Russian Republic near the Caspian Sea, are digging into the lives of the accused bombers and their family to identify possible terrorist ties.

Russian President Vladimir Putin told reporters Thursday that he regretted information Russia provided the United States concerning a 2011 trip that Tamerlan Tsarnaev took to Dagestan and Chechnya could not offer "operative significance," according to a transcript of the remarks provided by the Kremlin.

Russia's fear, that Tamerlan Tsarnaev would enlist in a militant group there came after the six months he spent in Dagestan and Chechnya. Upon his return to Massachusetts he posted a YouTube video glorifying a militant leader named Abu Dujana, who until Russian forces killed him last year led an Islamist-tied group in Dagestan, a source said.

Tamerlan Tsarnaev included the Dujana video in a YouTube channel dedicated to celebrating jihadis. Also on the channel was a video of Feiz Mohammad, an extremist preacher in Australia, the source said. Feiz Mohammad calls Jews "pigs" and rhapsodizes about killing them, encourages young Muslims to slaughter nonbelievers, and preaches that Muslim parents should aspire to have their children die as martyrs.

"All of that footage is being looked at," the source said of Tsarnaev's YouTube videos.

'Lies and hypocrisy'

In an Associated Press interview from Dagestan, Tsarnaeva -- who once lived in the United States -- denied having any terrorist link but said she wouldn't be surprised if she was on the watch list, which contains more than 500,000 names.

"It's all lies and hypocrisy," she said. "I'm sick and tired of all this nonsense that they make up about me and my children. People know me as a regular person, and I've never been mixed up in any criminal intentions, especially any linked to terrorism."

There is an outstanding U.S. warrant for her arrest for fleeing a 2012 shoplifting charge in Natick, Mass., which accuses her of stealing $1,624 worth of women's clothes there from a Lord & Taylor department store, according to the AP.

Meanwhile, investigators spent a fourth day sifting through tons of waste at the 39-acre Crapo Hill landfill in New Bedford, Mass. They're looking for emptied pyrotechnic shells that are used to make bombs, as well as a laptop computer, one of the sources said.

If found, the computer could allow investigators to locate emails, contacts, downloaded files and online browsing history, though some of that information has already been obtained from Internet service providers. Investigators have also located at least one other computer connected to the case, the contents of which have proved valuable, the source said.

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