The three New Bedford suspects will probably not be charged unless authorities can prove they knew ahead of time about the bombs, or knew where the younger Tsarnaev was hiding. But the Daily Mirror in London is reporting that the FBI is on the trail of a “12-strong terrorist ‘sleeper cell’ linked to brothers Tamerlan and Dzhokhar Tsarnaev”:

The FBI was last night hunting a 12-strong terrorist “sleeper cell” linked to the Boston marathon bomb brothers.

Police believe Tamerlan and Dzhokhar Tsarnaev were specially trained to carry out the devastating attack.

More than 1,000 FBI operatives were last night working to track down the cell and arrested a man and two women 60 miles from Boston in the hours before Dzhokhar’s dramatic capture after a bloody shootout on Friday.

A source close to the investigation said: “We have no doubt the brothers were not acting alone. The devices used to detonate the two bombs were highly sophisticated and not the kind of thing people learn from Google.

“They were too advanced. Someone gave the brothers the skills and it is now our job to find out just who they were. Agents think the sleeper cell has up to a dozen members and has been waiting several years for their day to come.”

A specialist team of CIA and FBI interrogators was yesterday flown to a Boston hospital to grill wounded Dzhokhar, 19, about the secret group. The University of Massachusetts student was caught on Friday after hiding out in a boat parked in a garden in locked down Watertown the day after a gun battle with police left his 26-year-old brother and a rookie cop dead.

Dzhokhar is said to have run his brother over as he escaped in a stolen car while Tamerlan lay handcuffed on the ground. They were carrying six bombs with them at the time, three of which ­exploded, as well as a handgun and rifle. The devices were thought to be pipe bombs.

Last night Dzhokhar – badly wounded but alive – lay handcuffed to his hospital bed under armed guard. The other three arrested in the port of New Bedford are also believed to be of college age.

Caution: I have been unable to find any other media outlet that is independently reporting this story. Any mentions of a sleeper cell associated with the brothers references the Mirror article. This is either a ginormous scoop by the Mirror or a tabloid fantasy.