LOS ANGELES, May 25: The US Federal Bureau of Investigation on Tuesday apologized to an American lawyer mistakenly detained for two weeks on suspicion of involvement in the deadly Madrid train bombings.

The FBI apology came after a US federal judge on Monday threw out the case against attorney Brandon Mayfield, 37, four days after he was freed from jail after being dramatically held in an embarrassing case of mistaken identity resulting from a fingerprint mismatch.

"The FBI apologizes to Mr Mayfield and his family for the hardships that this matter has caused," a statement from the US federal police agency said. Mayfield, a Muslim convert who became known for defending terror suspects in his home city of Portland, Oregon, was picked up by authorities on May 6 after he was linked to a fingerprint found on a bag containing detonators and explosives found at a site linked to the March 11 terror bombings in Spain.

"Soon after the submitted fingerprint was associated with Mr Mayfield, Spanish authorities alerted the FBI to additional information that cast doubt on our findings," the FBI said.

"Upon review it was determined that the FBI identification was based on an image of substandard quality, which was particularly problematic because of the remarkable number of points of similarity between Mr Mayfield's prints and the print details in the images submitted to the FBI," it said.

The bureau said its Latent Fingerprint Unit would review its practices and consider adopting new guidelines for its experts examining latent fingerprints taken from items which they do not have in their possession.

"We need to know more about how this happened," said public defender Steve Wax, who represented Mayfield. "All of us in this country need to know more about how this type of mistake can be made," he was quoted as saying by local media. -AFP