The hunt for clues for those who recruited, financed and supplied the four suicide bombers who blew up three underground trains and a double-decker bus in London on July 7 has now focused on the men's ties to Pakistan.

Prime Minister Tony Blair warned yesterday of the "evil ideology" of Islamic extremists bent on inflicting terror as authorities in three continents conduct investigations, and officials in Egypt said they would not hand over a biochemist detained in connection with the bombings.

Officials have confirmed that fifty-five people have died in the explosions. The hunt for clues continues, as police in Leeds searched an Islamic shop, the home of an Egyptian biochemist and another address for more evidence after investigators reportedly found traces of explosives in the man's bathtub.