Police in Britain (search) and Italy questioned 21 suspects as they sought to piece together the networks behind the London bombings, probing for possible links between the two sets of attacks and for connections to any accomplices overseas.

Investigators arrested seven people Sunday at a four-story brick apartment building in Brighton, on England's southern coast, and also searched another home in the city. They gave few details about what role the six men and seven women were suspected of playing in the failed July 21 attacks on the catacking three London Underground trains and a red double-decker bus.

A spokeswoman for London's Metropolitan Police said investigators believed there were more people at large who played some role in the attacks.

"It's extremely likely there will be other people involved in harboring (suspects), financing and making the devices," she said, speaking on condition of anonymity, because the department does not allow her to give her name.

In Italy, authorities were pursuing contacts linked to Osman Hussain (search), 27, who was arrested in Rome on Friday and is suspected of trying to bomb the Shepherd's Bush subway station in west London.

Police have discovered that Hussain called Saudi Arabia (search) hours before his arrest, the Sunday Telegraph newspaper reported. The Sunday Times said another bombing suspect — Ethiopian-born Briton Muktar Said Ibrahim, 27 — took a monthlong trip to Saudi Arabia in 2003, telling friends he was to undergo training there.

Britain was facing questions about how Hussain slipped out of the country five days after the attempted attacks, despite a massive police manhunt. Italy's Interior Minister Giuseppe Pisanu says Hussain, also known as Hamdi Issac, left London's Waterloo station by train for mainland Europe on July 26.

The Home Office said British immigration officials generally do not check the passports of people leaving the country. However, police asked that checks be made at many departure points, including Waterloo, after the attacks, a Home Office spokesman said on condition of anonymity.

The Sunday Times said only French officials had checked Hussain's passport as he left Britain, but the Home Office spokesman said British immigration officials had been checking all international departures at Waterloo the day he left.

Geoff Hoon, the leader of the House of Commons, said he realized there was concern about whether the checks were stringent enough.

"I am aware that the Home Office will be looking at that," he told British Broadcasting Corp. television. "I understand the criticism. It's important that we are able to identify those coming into the country as well as those leaving."

Police had released closed-circuit television images of the four bombing suspects shortly after the attacks, but the picture of Hussain, whose name was not made public until his arrest, was grainy and difficult to make out, his face shielded by a dark baseball cap. Police put out a second, clearer, image of him a day after his escape.

Italian news reports said Hussain's real name was Hamdi Issac and that he was from Ethiopia, not Somalia. He falsely listed his country of origin as Somalia when he applied for asylum and citizenship in Britain, the reports said.

Hussain was arrested Friday in Rome at the apartment of his brother Remzi Issac, who also was detained.

On Sunday, Italian police detained a second brother of Hussain, Fati Issac, for questioning, the Italian news agency ANSA said. Fati Issac was accused of destroying or hiding documents sought by investigators but is not alleged to have plotted terror, ANSA said

Britain has requested Hussain's extradition, which his court-appointed lawyer, Antonietta Sonnessa, said he is likely to fight.

She said Hussain acknowledges his involvement in the failed attack but claims the planted bombs were intended not to kill anyone but only to draw attention. Italian news reports had said the bombers were angry about the Iraq war.

"He has justified his actions as a form of protest against the fact that civilians are suffering in wars at the present time," she told Britain's ITV News.

Hussain also said his cell was not linked to either Al Qaeda (search) or the July 7 cell, Italian media reported.