British anti-terror police arrested four people in the city of Birmingham Wednesday morning, including a man identified as one of the suspects in last week's failed attack on London's transportation system.

Police said one of the arrested men was Yasin Hassan Omar, a 24-year-old immigrant from Somalia who is suspected of trying to blow up a London subway train on July 21 with a backpack bomb.

Omar reportedly resisted police and was subdued with a Taser stun gun after about 50 officers raided a home in Britain's second-largest city at 4:30 a.m.

A spokesman for the metropolitan police in London said authorities recovered a package during the Birmingham raid that was being examined as a possible explosive device.

Police planned to carry out a controlled explosion to destroy the device, and about 100 homes in the neighborhood were evacuated.

The arrests took place at two different locations in Birmingham, which is about 120 miles northwest of London. Police said the operations were connected to the investigation of the attempted bombings on July 21 of three subway trains and a bus in London.

The police spokesman said the first man arrested, later identified as Omar, was brought to the high-security Paddington Green police station in central London. The other three were being held in custody in Birmingham.

The BBC reported that Omar was wearing a backpack at the time of his arrest.

According to Britain's Home Office, Omar, the son of Somali refugees, arrived in Britain in 1992 at age 11 and obtained British residency.

Another man being sought for last week's bombings is Muktar Said Ibrahim, 27, an immigrant from Eritrea who was granted British citizenship in 2004, the Home Office said.

Police launched a manhunt after the July 21 attempted bombings and released images of Omar, Ibrahim and two other men thought responsible for the abortive attack. The other two men so far have not been publicly identified.

Police have been trying to determine whether last week's failed bombings were connected to the deadly July 7 attacks that killed 52 people and the four suicide bombers who carried them out.

In a separate development, two other men were arrested on suspicion of terrorism while traveling on a train in England's Midlands region, wire services said.

The Birmingham arrests bring to nine the number of people that police have said are being held in connection with the July 21 attempt. Police last week arrested five other people.

Fred Barbash reported from Washington.