British police dispatched reinforcements to patrol London's subway to discourage more suicide attacks.
The officers in neon yellow jackets have been flooding the subway network - hoping their visibility will reassure a public jittery since July 7 attacks on three subway trains and a bus killed 56 people, including four suicide bombers. New officers were brought into the mix to help relieve exhausted colleagues, who stepped up patrols last week as part of their biggest operation ever.
"It's a fair challenge to keep it going," said Simon Lubin, the transport police spokesman. "We brought people in from other parts of the country to give us some rest."
British media speculated that a third cell was waiting to be activated, but a spokeswoman for London's Metropolitan Police played down the reports. "We can't guarantee that there won't be a third attack, but we have never talked about a third cell," the spokeswoman said on condition of anonymity, because her department does not allow her to be quoted by name, the AP reports.
Since the July 7 attacks and a failed copycat operation on July 21, police have repeatedly warned the public that more attacks were possible.
Hoping to avert further attacks, investigators interrogated three men suspected in the July 21 attacks on three subway trains and a double-decker bus, while an Italian judge on Monday began questioning the fourth alleged attacker after he was detained Friday in Rome.
Britain has requested that Italy extradite Hamdi Issac, 27, who is suspected of trying to bomb the Shepherd's Bush subway station in west London. Issac's lawyer has said her client is likely to fight the extradition bid.
Italian police gave a briefing Monday detailing how they tracked Issac to his brother's apartment in the Italian capital. They also said the Ethiopian-born suspect had used the fake name Osman Hussain and claimed he was a Somali in order to claim refugee status in Britain in 1996. They said they expected to extradite him to Britain in a short time.
Italian newspaper Il Messaggero reported Monday that Issac started becoming a fundamentalist after attending London's Finsbury Park mosque, which previously has been linked to radical Islamic activity.
At the time he also met and became friends with Muktar Said Ibrahim _ who also is being held over the failed July 21 bomb attacks _ at a gym on the outskirts of London's Notting Hill district, according to Il Messaggero.
The two watched footage of the war in Iraq, the Rome-based paper said. It reported that Issac told investigators that the pictures prompted him to take part in the attempted attacks.
Issac was arrested in Rome at the apartment of his brother Remzi Issac, who also was detained. Italian police have also detained a second brother, Fati Issac, for questioning.
Police say the four suicide bombers who carried out the July 7 attacks, which killed 52 victims, are all dead. And they believe they have arrested all the failed July 21 bombers, whose explosives detonated only partially and took no lives.
In total, British officers are holding 18 suspects in connection with the July 21 attacks, including six men and a woman arrested Sunday in Brighton, on England's southern coast.
Now they are searching for those who may have recruited and directed the attackers and built the explosives, anxious to catch them before they _ or other would-be bombers they command _ strike again.
Investigators are also searching for links between the two terror cells, one made up mostly of Pakistani Britons and the other mainly of east African immigrants to London. The groups struck exactly two weeks apart, each attacking three London Underground trains and a red double-decker bus.
The Metropolitan Police spokeswoman 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.
Hamdi Issac's lawyer, Antonietta Sonnessa, says her client acknowledges his involvement in the failed July 21 attack, but claims the planted bombs were intended not to kill anyone, but only to draw attention. Italian news reports said the bombers were angry about the Iraq war.
Issac also said his cell was not linked to either al-Qaida or the July 7 cell, the AP reports.