An Egyptian chemistry student has been arrested in connection with last week's London bombings. Thirty-three-year-old Magdy Elnasher was arrested in Cairo. An Egyptian ministry statement says Elnasher has denied any involvement in the bombings that killed 54 people.

Meanwhile, authorities are investigating a possible link between the al-Qaida network and the bombers.

Egyptian officials say police arrested Magdy Elnasher , a chemist who studied in the United States at North Carolina State University, and at Leeds University, where he taught recently.

Leeds University says he arrived in October 2000 to do biochemical research and earned his doctorate in May of this year. 

British newspapers say he rented a house in Leeds that was raided by police Tuesday. Large amounts of what are believed to be explosives were seized.

Police are also focusing on the Leeds home of the youngest alleged bomber, 18-year-old Hassib Hussain. Investigators say he set off the bomb that ripped apart a double-decker bus at Tavistock Square, killing 14 people. Police questioned one of Hussain's relatives Friday.

Police Commissioner Sir Ian Blair told British radio he believes police will uncover a "clear" al -Qaida link.

Western news agencies are quoting Pakistani intelligence officials, who say investigators are focusing on a possible connection between 22-year-old suspect Shahzad Tanweer, and two al-Qaida-linked groups in that country. Three of the four bombers -- including Tanweer -- were British Muslims of ethnic Pakistani origin.

Sources say investigators believe that within the past year, Tanweer visited a radical Muslim school in Pakistan. That school is run by a Sunni group, Lashkar e-Tayyaba, banned by President Pervez Musaharraf for its alleged role in a 2001 attack on India's parliament.

Investigators also reportedly believe Tanweer may have visited Pakistani militant Osama Nazir, arrested for his role in a deadly grenade attack on an Islamabad church in March 2002.

Meanwhile, British officials continue to hunt for another British-born man of Pakistani descent with possible links to al-Qaida. They think he could be the mastermind of the attacks.