LONDON — British counterterror police have arrested two more people 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 on Wednesday 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.

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

The homemade explosive device, placed inside a bucket that was enclosed by a shopping bag, injured 30 people when it partially detonated inside a subway car last week.