Moscow - A delegation from the US embassy in Moscow has travelled to the Russian North Caucasus region of Dagestan to interview the parents of the Boston marathon bombing suspects, an embassy official said on Wednesday.
The parents of Tamerlan and Dzhokhar Tsarnaev are currently living in Dagestan, an overwhelmingly Muslim region on the Caspian Sea where the family briefly lived before leaving for the United States.
"The FBI is receiving co-operation from the Russian government in its investigation of the Boston marathon bombing," a US embassy official, who asked not to be named, said.
"A group from the US Embassy in Moscow travelled to Dagestan yesterday [Tuesday] as part of this co-operation with the Russian government to interview the parents."
The official declined to say whether the delegation was still in Dagestan. It was not immediately clear if the interviews had already taken place.
Tamerlan, aged 26, was killed in a shootout with US police while Dzhokhar, 19, was gravely wounded during his capture last week. He remains hospitalised and has been read the charges of using and conspiring to use a weapon of mass destruction.
The brothers' father Anzor, an ethnic Chechen born in Kyrgyzstan, has repeatedly said in media interviews that his sons were innocent and could not have carried out the bombings. Their mother Zubeidat hails from Dagestan itself.
The trip by the US delegation to Dagestan comes amid mounting questions in the United States about whether the US authorities missed crucial signals that should have raised suspicion about the two brothers before the bombings.
Particular interest has surrounded trip of around six months made by Tamerlan in 2012 to Dagestan and Chechnya.
Russian security sources in Dagestan have told AFP he was seen four times with a figure suspected of links with the Islamist underground during his visit but there was never any reason to apprehend him.
The two brothers, who had been living in the United States for over a decade, are accused of the twin marathon bombing on 15 April, which killed three people and wounded more than 260 others.