Police in Britain say a second man has been arrested in connection with a bomb attack on the London metro that injured more than two dozen.
The capital's Metropolitan Police said on September 17 that the 21-year-old man, who was not identified, was arrested in Hounslow, west London, late on September 16.
The announcement comes after police said they had evacuated a residential address in the small town of Sunbury, southern England, and were searching the property.
A suspect in the subway bombing was detained in the port city of Dover on September 16 in what they described as a "significant" development.
A bucket packed with nails and explosives blew up on a crowded subway train at London's Parsons Green station on September 15, injuring 30 people.
The station has reopened for service.
Meanwhile, Britain’s terror threat level was downgraded from critical to severe after the investigation into the attack progressed.
“Following the attack on Parsons Green last Friday, the police have made good progress with what is an ongoing operation," Home Secretary Amber Rudd said in a September 17 televised statement.
"The Joint Terrorism Analysis Center, which reviews the threat level the U.K. is under, has decided to lower that level from critical to severe,” Amber added.
Severe, the second highest level, means an attack is highly likely.
The Islamic State extremist group, through its Amaq propaganda agency, claimed responsibility for the attack, the fifth in Britain this year. But police said that claim could not be verified.