By Paisley Dodds,Associated Press Writer

LONDON – Police swooped down on a posh London neighborhood and traced cell phone calls across Europe to a Rome hide-out Friday, netting the remaining suspects in the failed transit bombings without firing a shot. The arrests capped an eight-day manhunt that was one of the most extensive in British history.

At least three of the four suspects were of East African origin.

Black-clad police armed with stun grenades and gas masks pointed assault rifles at the doors of suspects on the outskirts of Notting Hill. Two young children stumbled into the standoff a floor below a suspects’ apartment, and an armed officer tried to shoo them away from his dog.

Above them, a police team shouting for “Mohammed” forced two suspects to strip to their underwear and eventually emerge onto a narrow balcony, where television cameras recorded them with their hands above their heads.

In Rome, police arrested a Somali-born British citizen at the apartment of his brother, who was also taken into custody. On Friday night, a police expert – wearing white gloves and a jumpsuit to avoid contaminating possible evidence – could be seen working inside a lighted room in the apartment.

Images captured on closed-circuit television cameras during the failed July 21 attacks helped lead investigators to the men, and interrogations of the suspect captured first, 24-year-old Yasin Hassan Omar, may have helped as well. Police said the anti-terrorist sweeps have been part of their most extensive investigation ever.

Peter Clarke, head of Scotland Yard’s anti-terrorist branch, sounded a cautionary note as he announced the arrests.

“Despite the progress that has been made with the investigation, we must not be complacent,” Clarke warned. “The threat remains, and is very real.”

Authorities have been looking for a link between the failed July 21 attacks and the July 7 suicide bombings, which killed 56 people, including the four bombers. Three of the suicide attackers had links to Pakistan.

They have a working hypothesis that the cells did not know each other, but were connected by a more senior operative higher up an organizational chain, said a counterterrorism official, who spoke on condition of anonymity because investigations are ongoing.

Authorities also are theorizing the plot may be linked back to Pakistan and the al-Qaida organization there. However, “we are not there yet in terms of proving it,” the official said.

The official said the newly detained individuals are being questioned, and authorities haven’t ruled out that additional cells may be on the loose. It’s also not yet clear precisely why a team of young men of mostly Pakistani descent and a second team of African men were put together.

A British police official said of any potential cell links: “Yes, it is possible they may not have been known to each other but had a conduit working between them for someone else.”

On the links back to Pakistan and al-Qaida, the official said it was too early to make that connection and noted police have 20 people in custody for questioning, with the inquiry expected to last several months. The official was not authorized to give his name.

One man arrested in the apartment complex near Dalgarno Gardens street identified himself as Muktar Said Ibrahim, 27, Clarke said. Police believe he planted explosives on the No. 26 bus in Hackney, east London. Ibrahim, also known as Muktar Mohammed Said, immigrated from Eritrea in 1990 and became a British citizen in 2004.

The second man arrested at the complex identified himself as Ramzi Mohammed, Clarke said, and police accuse him of carrying explosives into the Oval Tube station. He was shown on closed-circuit footage wearing a “New York” sweatshirt.

On Wednesday, police in Birmingham arrested Omar, a Somali citizen with British residency who is suspected of trying to blow up the Warren Street subway station.

A third man was arrested at the Tavistock Crescent apartment complex, also on the outskirts of Notting Hill. Police would not release any details about him except to say he was not seen in the closed-circuit TV images.

Investigators speculated a fifth bomber was involved after finding an unexploded bomb in a park near where Friday’s raids occurred.

A fourth man – identified as Somali-born Briton Osman Hussain – was arrested in Rome, Italian authorities said. Hussain is accused of planning to plant a bomb at Shepherd’s Bush Underground station in west London. He was seen on closed-circuit television carrying a backpack.

Clarke said Britain will ask Italy to extradite him.

London police told Italian officials a call intercepted at one of the botched bombing sites came from a cell phone that belonged to someone in Rome, RAI state TV reported. Two days ago, the cell phone moved from London to Paris, then Milan, then to the apartment in Rome, RAI said.

Cellular phones tied to a regular account are easier to trace than calls made from cell phones using anonymous prepaid cards.

Italian police raided the apartment Friday, where they found Hussain with the cell phone, RAI said. The Italian news agency ANSA said he offered no resistance.

The raids near Notting Hill lasted for nearly four hours and began when neighbors heard a loud explosion and cracks that sounded like shots.

Police shouted at the suspects in one apartment, calling for “Mohammed” to emerge, said one witness, Nicolas Holliman.

“He was being asked to come out with his hands up, naked or in underclothes,” Holliman said. “They were … telling him he would be safe if he puts his hands up.”

They also shouted warnings: “You’re going to be dead unless you open up this door!”

Police pointed assault rifles at the door, a witness said. Other officers wearing black balaclavas and body armor surrounded the building and went door to door in the neighborhood, famous for its weekend street market, and told people to leave.

Some witnesses heard several explosions – possibly stun grenades or tear gas. Helicopters buzzed overhead and police cordoned off a number of streets.

Separately, two women were taken into custody at London’s Liverpool Street train station under anti-terror laws. It was not clear whether they were detained in connection with the attacks. One woman was believed to have been in line for the Stansted Express, which goes to an airport outside London, when she was arrested.

Scotland Yard declined to comment on the arrest in Zambia of a British man sought in connection with the July 7 bombings. British investigators reportedly believe Haroon Rashid Aswat, 31, had been in telephone contact with some of the four suicide attackers.

Aswat told investigators he once was a guard for Osama bin Laden, Zambian security officials said.