Birmingham, England ? Police stormed a brown-brick duplex Wednesday and used a stun gun to arrest a Somali suspected of being one of four men behind botched attacks in London – a breakthrough that could yield the inside story on terror bombings that set the British capital on edge.

Yasin Hassan Omar, 24, was carted to a top-security police station in London, and a key official called the arrest significant – but warned that until all the bombers were in custody, the threat remained.

Dozens of anti-terrorist police and bomb disposal experts, some in heavy body armor, swept into a neighborhood of Britain’s second-largest city to arrest Omar, a Somali citizen with British residency who is suspected in the botched July 21 attack on the Warren Street subway station.

“They had him dressed in one of those white suits. He had plastic cuffs on the front,” said one neighbor, Andy Wilkinson, who recognized Omar from police images of suspects. Police use such suits to preserve physical evidence that may be on a suspect.

Police also detained three other men at a house about two miles away, saying the arrests were linked to the second set of failed bombings, but declining further comment. In all, eleven suspects are being held, though only Omar is thought to be one of the bombers, police said.

Interrogations of Omar may be key to determining whether the second set of bombings July 21 are linked to the July 7 suicide attacks that killed 56 people, including the four bombers.

ABC News, meanwhile, reported that British authorities investigating the July 7 attack had found 12 bombs and four improvised detonators in the trunk of the car of one of the suspected suicide bombers 35 miles outside of London five days after the deadly explosions.

The network broadcast photos of the findings, including a glass bottle apparently packed with explosives and covered in nails that could be used as shrapnel, and said they provided important clues about who was behind the attacks.

After arresting Omar, police evacuated up to 100 homes and sent a bomb squad into the Small Heath neighborhood in Birmingham, a city some 120 miles northwest of London.

They allowed a few residents to pick up belongings during the day, but kept up cordons near Omar’s rundown house next to a sprawling park.

Kati Stewart, 31, a health care worker who lives across the street from Omar, said she’d seen four men coming and going frequently over the past two weeks. “They would come at 2 a.m., and then when you looked in the morning, the car had gone,” she said.

But Omar generally attracted little attention in the diverse neighborhood, where residents of many ethnic backgrounds and faiths – Indian, Pakistani and Irish; Christian, Hindu and Muslim – say they live together peacefully.

Other raids were carried out Wednesday in south London’s Stockwell district, where officers arrested three women on suspicion of “harboring offenders,” and on two more London homes, where no arrests were made but forensic tests were conducted, police said.

Police were still seeking three other men believed involved in the failed bombing attempts.