British police have released all but one of the seven suspects they arrested over the recent attack on a London subway train.
The three men released Tuesday face no further police action.
The only person still in custody is 18-year-old Ahmed Hassan, who has been charged with attempted murder and other crimes.
The investigation of the Sept. 15 attack on a train at Parsons Green station has been wide-ranging
A homemade bomb filled with lethal shrapnel partially exploded, injuring 30 people during the rush hour commute. Officials said the casualty toll would have been far higher if it had fully detonated.
The Islamic State extremist group claimed responsibility but British officials have not confirmed its role.