A man arrested in connection to the Parsons Green explosion has been released without charge, police have said.
Yahyah Farrouk, who was arrested in Hounslow on Saturday 16 September was released on Thursday and is no longer a suspect in the investigation.
Mr Farrouk, a 21-year-old Syrian national, was the only named suspect in the investigation.
He was one of two refugees fostered by the same couple to be arrested on suspicion of terror offences in relation to the attack.
The other, an unnamed 18-year-old Iraqi refugee, was arrested in Dover last Saturday while allegedly trying to board a ferry to France.
They were both fostered by Sunbury-on-Thames couple Penelope and Ronald Jones, aged 71 and 88 respectively. The couple were awarded MBEs in 2009 for their services to children and families.
A further four men remain in custody in connection to the attack that left 30 injured after an explosion rocked a District Line Tube train.
Three men aged 25, 30 and 48 were arrested in Newport, South Wales, this week, and a 17-year-old was arrested on Thursday in Thornton Heath in south London.
Commander Dean Haydon, head of the Metropolitan Police counter terrorism command, said: “This continues to be a fast-moving investigation. A significant amount of activity has taken place since the attack on Friday.
“We have five males in custody and searches are continuing at four addresses. Detectives are carrying out extensive inquiries to determine the full facts behind the attack.
“We anticipate that the searches will take some days to complete and may cause further disruption. However, it is important that we continue with these searches and Id like to thank all those affected for their support, patience and cooperation.”