LEEDS, England - Police in Egypt questioned a biochemist about the London subway bombings, trying to decide whether to hand him over to British investigators after authorities in this northern town reportedly found traces of explosives in his bathtub.
In another sign of the investigation's widening global reach, Metropolitan Police Commissioner Sir Ian Blair said authorities were trying to determine whether any of the four "foot soldiers" - the suicide bombers who ranged in age from 18 to 30 - had ties with Pakistan-based cells of the al-Qaida terror network.
In an interview with British Broadcasting Corp. radio, Blair said the inquiry was focusing on the organizers of the attacks, and he confirmed that police were most interested in the Pakistan connection. The bombings of three subway trains and a bus killed 55 people, including the bombers. Police increased the death toll from 54 after another victim died in the hospital overnight.
Three of the bombers - Shahzad Tanweer, Mohammed Sidique Khan and Hasid Hussain - were Britons of Pakistani origin. At least two had traveled to Pakistan.
Prime Minister Tony Blair said Saturday that authorities were facing an "evil ideology" in their struggle against Islamic terrorism.
"The greatest danger is that we fail to face up to the nature of the threat that we're dealing with," he said during a speech in London. "And what we are confronting here is an evil ideology. ... It is a battle of ideas, of hearts and of minds, both within Islam and outside it."
He also insisted there was no link between Islamic terrorism and the situation in Iraq, where Britain is the second-largest partner in the coalition, or the conflict between Israel and the Palestinians.
British media have reported that Khan, 30, visited the Houses of Parliament last year as the guest of Labour Party lawmaker Jon Trickett.
Two senior Pakistani intelligence officials said Friday that authorities there were looking into a possible connection between Tanweer and two al-Qaida-linked militant groups, and in particular a man arrested for a 2002 attack on a church near the U.S. Embassy in Islamabad.
On Saturday, intelligence and school officials said Pakistani authorities questioned several students, teachers and administrators at one of two religious schools - or madrassas - believed visited by Tanweer.
Asad Farooq, a spokesman for the Jamia Manzoorul Islam seminary in central Lahore, acknowledged in an interview that intelligence agents were there Saturday, but he denied that Tanweer had ever been at the school.
British police on Saturday continued searching a shop called Iqra Learning Centre in the Leeds neighborhood of Beeston. The shop, which officers raided Friday, appeared to sell Islamic books and DVDs and offer seminars and presentations.
Two investigators wearing white protective suits were seen inside the store before officers covered the windows with gray plastic sheeting. The immediate area remained cordoned off.
The shop is about four miles from Egyptian chemist Magdy Mahmoud Mustafa el-Nashar's town house, where British news media reported that police found evidence of the explosive TATP inside a bathtub. Police continued searching the house Saturday from behind large black and white sheets draped from scaffolding.
TATP was used by Richard Reid, whose attempt to blow up a trans-Atlantic flight from Paris to Miami in December 2001 with explosives in his shoes was thwarted. Reid pleaded guilty to U.S. charges and is serving life in prison.
Egypt's Interior Ministry announced Friday that Egyptian authorities were interrogating el-Nashar, who had studied for one semester at North Carolina State University and taught at Leeds University, where he earned his doctorate in May. It said el-Nashar denied having any connection to the attacks.
An Egyptian government official said el-Nashar, 33, was arrested in Cairo on Sunday or Monday after British officials informed Egypt of their interest in him. The official spoke on condition of anonymity because he was giving information not in the official ministry announcement.
But el-Nashar's youngest brother, Mohammed, said he was arrested Thursday when he went to a local mosque to pray but didn't return.
In London, Ian Blair said British authorities would seek his extradition, if need be, although the two countries do not have an extradition treaty.
A security official in Cairo said Britain was pressing Egypt to hand over el-Nashar, but Egypt was trying to determine if there was enough evidence against him to do so. The official spoke on condition of anonymity because the information was not authorized for official release.
Britain's Foreign Office had no comment on the security official's statement.
The Egyptian Interior Minister said el-Nashar came to Egypt from London on vacation and intended to return to Britain.
"He pointed out (to questioners) that all his belongings remained in his apartment in Britain," the ministry said.
In Leeds, authorities searched el-Nashar's townhouse in a complex of two-story brown brick apartments. The home was surrounded by blue-and-white police tape and covered in scaffolding draped in white plastic sheeting. Forensic teams in white coveralls carted out material.
TATP, or triacetone triperoxide, is a highly unstable explosive made from commercially available chemicals.
Andy Oppenheimer, an explosives expert with Jane's Information Group, said TATP is strong enough to have caused the damage wreaked by last week's bombs. But he said making such a highly volatile explosive stable enough to carry out closely synchronized attacks would have required advanced knowledge of chemistry. Police say the three subway blasts happened within a minute.
El-Nashar's research at Leeds focused on biocatalysis and enzyme immobilization, according to a biography of him at the university's Web site.
That kind of research "wouldn't have anything directly to do with explosives" or with biological weapons, said Constance Ann Schall, an associate professor at the Chemical Engineering Department at the University of Toledo in Ohio.
Meanwhile, the families of Khan and Hussain - the 18-year-old believed to have blown up the double-decker bus - issued statements saying they were devastated by the attack and had no idea he could have been involved.
Hussain's family said it was unaware of his activities and "would have done everything in our power to stop him" had it known.
Khan's family expressed "deepest and heartfelt sympathies" for the victims and insisted Khan must have been "brainwashed" to have been involved. The family called on people to "expose the terror networks which target and groom our sons to carry out such evils."