LONDON — British counterterror police arrested two more people Wednesday in relation to the London subway attack, bringing the number to five.

Detectives arrested a 48-year-old man and a 30-year-old man under the Terrorism Act in Newport, Wales. A 25-year-old man was also arrested in Newport on Tuesday.

Two other men arrested over the weekend — an 18-year-old refugee from Iraq and a 21-year-old from Syria — remain in custody. Neither has been charged.

Extensive inquiries are ongoing and searches are ongoing at four addresses.

“We anticipate that the searches will take some days to complete and may cause further disruption,” said Dean Haydon, head of the Metropolitan Police Counter Terrorism Command.

A homemade bomb planted in a rush-hour subway car partially detonated Friday, injuring 30 people. The attack sparked a huge manhunt for the perpetrators, and prompted the British government to briefly raise the national terrorism threat to the highest level.