One of seven people arrested in a Metropolitan Police counter-terrorism operation has been released without charge.
The 30-year-old woman had been arrested in west London on Thursday.
Six other people are still being held in custody.
Police say the operation is not linked to the Olympics or Paralympics.
Police have arrested a seventh person as part of an ongoing investigation into a suspected terror plot.
A 22-year-old woman was detained at a residential address in Hackney, east London, early today.
She was arrested on suspicion of the commission, preparation or instigation of acts of terrorism under the Terrorism Act 2000, a spokesman for the Metropolitan Police said.
The arrest, by officers from the Met's Counter Terrorism Command, follows six others made on Thursday.
A British Muslim convert who appeared in a BBC documentary was reportedly one of six people arrested over a suspected terror plot - including three living just over a mile from the Olympic site.
Richard Dart, 29, who changed his name to Salahuddin al-Britani after converting, was said to have been one of three people detained in Ealing, west London, yesterday morning. He was arrested in the street.
The others detained in Ealing were a 21-year-old man and a 30-year-old woman held at separate home addresses.
Police are continuing to question six people arrested in London yesterday over a possible terror plot involving Islamist extremists. They include three brothers who live in a house just a mile from the Olympic stadium.
An investigation involving MI5 is behind today's raids in London, which have led to the arrests of six people suspected of terror offences. It's thought the operation centres on a plot involving Islamist extremists with potential targets in Britain. Addresses right across London are being searched.
The operation is understood to relate to a possible plot involving Islamist extremists with potential targets in the UK.
The threat was not thought to be imminent.
Some of those arrested are understood to be British nationals.
The six were taken to a south-east London police station, the force spokesman said.
A 29-year-old man was arrested in the street in west London, a 21-year-old man and the women were arrested at a separate residential premises in west London, and three other men, aged 18, 24, and 26, were arrested in east London.
– Scotland Yard spokesperson
Searches under the Terrorism Act 2000 are being carried out at eight residential premises in east, west and north London and one business premises in east London.
Public safety remains our overriding concern.
Five men and a woman have been arrested in London on suspicion of the commission, preparation or instigation of acts of terrorism, Scotland Yard said today.