LONDON - British police said Sunday they had made a second arrest in connection with the bombing of a London Underground train, as their probe into the terror attack widened.
The 21-year-old man, who has not been named, was arrested late Saturday in Hounslow, on the western rim of the capital, a statement said.
Officers had earlier arrested an 18-year-old man over Friday's attack at Parsons Green station, which injured 30 people, and said they were hunting for more suspects.
The bomb detonated in a packed train carriage Friday morning with a large explosion followed by what an eyewitness described as a "fireball".
It was Britain's fifth terror attack in six months -- a series that has claimed 35 lives.
The Islamic State group claimed responsibility.
The first arrest on Saturday took place at the Dover ferry terminal -- a main link to Europe. A "number of items" were recovered during the operation and the teenager is now in custody in London, officers said.
Police had earlier raided a home in Sunbury, a town west of London. Local residents quoted in British media said the owners of the house were elderly foster parents.
- Terror threat 'critical' -
Britain's terror threat was raised on Friday to "critical", indicating that another attack is feared, and soldiers have been deployed to guard key points to free up police for the investigation.
The critical warning was last used after a deadly suicide attack at Manchester Arena, also claimed by IS, in May.