A U.S.-trained Egyptian chemist, interrogated by police in Cairo connection with last week's bombings in London, denies any involvement in the attacks.

Magdy el-Nashar, 33, was taken into custody in suburban Cairo at the request of Scotland Yard. "El-Nashar denied having any relation with the latest events in London," The Egyptian Interior Ministry said in a statement.

El-Nashar, whom British authorities have yet to formally call a suspect, left the United Kingdom two weeks before the transit attacks.

Police searched el-Nashar's Leeds town house and found evidence of the explosive TATP inside a bathtub, according to British news media.

TATP, or triacetone triperoxide, is the same explosive used by "shoe bomber" Richard Reid when he attempted to blow up a flight from Paris to Miami, just months after September 11, 2001. Reid is now serving life in prison.

Andy Oppenheimer, an explosives expert with Jane's Information Group, told The Associated Press that TATP is strong enough to have caused the damage in last week's attacks, which left dozens dead and hundreds wounded.

"Police are making a possible connection between him and the bomb-making factory that serviced the London (bombers who) came down from Leeds to carry out the bombs," BBC's Chris Cundy reported from Leeds, appearing on CTV's Canada AM.

"That bomb-making factory is about half a mile away from the flat in the Hyde Park district of Leeds where this Egyptian student was believed to have been living."

El-Nashar, who arrived at Leeds University in October 2000 to do biochemical research, earned a doctorate in May.

The FBI had also joined in the extensive worldwide manhunt for el-Nashar because he attended a university in North Carolina five years ago.

The al-Qaeda link

Meanwhile, Pakistani authorities were looking into a connection between one of the London suicide bombers and al Qaeda-linked militant groups.

Two senior intelligence officials told the Associated Press, on condition of anonymity, that they were investigating a possible link between 22-year-old Shahzad Tanweer and a man arrested for a 2002 attack on a church near the U.S. Embassy in Islamabad.

Tanweer is reported to have visited Pakistan in late 2004 and met Osama Nazir, who was arrested last December for the 2002 bombing.

Tanweer is also believed to have visited a radical religious school run by a banned Sunni Muslims militant group. However, officials disputed reports that Tanweer studied at the school.

On Thursday, British authorities confirmed that two of the four suicide bomb suspects -- Tanweer and 18-year-old Hasib Hussain -- were Britons of Pakistani descent.

According to reports, the other two suicide bombers have been identified as 30-year-old Mohammed Sidique Khan, also a Briton of Pakistani ancestry, and Jamaican-born Briton Lindsey Germaine.