One of seven people arrested in a Met Police counter-terrorism operation has been released without charge.
A 30-year-old woman detained on Thursday, when five men were also arrested, was freed on Saturday.
A 22-year-old woman became the seventh person arrested in the operation when she was detained in east London in the early hours of Saturday.
The arrests are on suspicion of the commission, preparation or instigation of acts of terrorism.
On Friday, a magistrate granted detectives additional time until 12 July to keep in custody those arrested the day before.
One of the six, who are aged between 18 and 30, had been Tasered by police.
Police continue to hold the five men and the woman arrested later at a south London police station.
Eight homes in west, east and north London and one business have been searched.
It is understood the arrests relate to a possible plot involving Islamist extremists, with potential UK targets.
Three of those held are brothers - one an ex-police community support officer.
He served with the Metropolitan Police for more than two years before resigning in September 2009.