The British police have released another man, detained in connection with the failed July 21 bomb attacks on London's [Images] transit system.

The man was released on Tuesday without any charge.

Of the 37 people detained for attempting to set off bombs on three subway trains and a double-decker bus, 21 were no longer being held in connection with the investigation. London's metropolitan police said on Wednesday that its officers were continuing to question the remaining suspects. 

British authorities said those who were still in custody included three of the failed bombers. They were trying to extradite the fourth suspected attacker, Hamdi Issac, from Italy [Images]. But his lawyer said Italian investigations could delay his extradition to Britain.

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