UK arrests 2nd suspect in London train attack, lowers threat level

LONDON — Britain lowered its security threat level from “critical” to “severe” Sunday after the arrests of two suspects in the terrorist attack on the London underground railway.

Police have made “good progress” in the investigation, Home Secretary Amber Rudd said. The new threat level still indicated that another attack was highly likely and that people should continue to be “vigilant.”

London’s Metropolitan Police said in a statement that the second terrorism suspect, a 21-year-old man, was arrested in west London late Saturday night.

Police have also detained an 18-year-old in the port city of Dover suspected of links to the bombing. Media reported that the suspect lived with foster parents in the town of Surrey near London, and that the elderly couple had fostered a number of children and youths in the same house.

A second home was searched on Sunday, also in Surrey near Heathrow airport, according to a police statement. No further information was available about the search.

The investigations were triggered after a bucket packed with nails and the explosive triacetone triperoxide was left on a busy train during Friday’s morning rush hour. It injured about 30 people when it went off, but no one died. One person remained hospitalized Sunday.

The detonation, considered by police to have been partial, was claimed by Islamic State.

Officials have said they are not sure how many people were involved in the bombing, which prompted the government to raise the country’s terrorism warning to “critical,” its highest level.