British police have made a second arrest in connection with the bombing of a London Underground train.
A 21-year-old man, who has not been named, was detained late Saturday in Hounslow, on the western rim of the capital, a police 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.
Home Secretary Amber Rudd said Sunday that police are trying to find out how the teenager “was radicalised”.
The bomb went off in a packed carriage and although the device is thought to have malfunctioned it still caused a large explosion followed by what eyewitnesses said was a “fireball”.
IS claims responsibility
The attack is Britain’s fifth terror attack in six months, which has claimed 35 lives. The Islamic State group claimed responsibility for Friday’s explosion.
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 also raided a home in Sunbury, a town west of London on Saturday. Local residents quoted in British media said the owners of the house were elderly foster parents.