Speculation is growing that one of the Boston bombers met a known Jihadist terrorist in 2011 - as it emerged the FBI failed to follow up on a Russian tip that he was seen with an Islamic militant six times.
On a YouTube account widely believed to belong to Tamerlan Tsarnaev, 26, there are two videos on a playlist called 'terrorists' created five months ago that since have been deleted.
Both videos appear under the name, 'Amir Abu Dujana rabbanikaly' which is also the name used by Gadzhimurad Dolgatov, a notorious Dagestani terrorist.
Investigators are pouring over the YouTube account to see if they can confirm whether Tsarnaev had any links with Dolgatov, who was killed by Russian security forces in Makhachkala in December 2012, after a fierce gun battle.
These latest revelations question the adequacy of the U.S intelligence community, who failed to spot the national security threat posed by suspect Tamerlan Tsarnaev and his younger brother Dzhokhar, despite the repeated warnings.
On Sunday, a Dagistani police official source revealed to NBC News that the Russian internal security service contacted the FBI in November with some questions about Tamerlan and handed over a copy of a case file on him.
The 26-year-old Chechen, who was living in the U.S. after being granted refugee status in 2002, first caught the eye of authorities after he was spotted meeting with a person involved in the militant Islamic underground movement in Dagestan. They met at a mosque on six occasions, the source said.
The source told NBC the militant and Tsarnaev disappeared before authorities could speak with them; they added that the FBI never responded. A senior law enforcement official said that the FBI's earlier investigation did not turn up anything and they did not have the legal authority to keep tabs on him.
The question law enforcement officials will be asking themselves is, did Tamerlan meet Dolgatov when he visited Makhachkala in 2011?
However, Christopher Swift, professor of national security studies at Georgetown University told CNN that these videos and the fact they were deleted reveal nothing concrete - just yet.
'There is no evidence that these young men were seeking to make a point about Chechnya per se.'
He said he believes it is more likely that they were trying to make a point about themselves, as if to say: 'We are warriors. we have been wronged, people do not understand us and we must be heard.'
The FBI has confirmed that Russia alerted the agency in 2011 that Tsarnaev had ties to 'radical Islam' groups in his homeland. Homeland Security sources have also revealed the agency received tips in 2012 about his ties to extremists connected to a Boston mosque.
Congress is now promising a full inquiry into what intelligence had been unearthed on the suspected bombers that could have alerted authorities.
Rep. Michael McCaul, the Chairman of the House Homeland Security Committee, called it 'disturbing' that the Chechen immigrant was 'on the FBI radar' in 2011 but was deemed to not be a risk to national security.