U.S. investigators suspect those who carried out deadly terror bombings in London last week remain alive, adding urgency to the investigation, Homeland Security Secretary Michael Chertoff said on Sunday. The United States has sent FBI agents with forensic expertise to help British authorities analyze the crime scene, which authorities in both countries say bear the hallmarks of the al Qaeda network that attacked the United States on Sept. 11, 2001, Reuters reported. "And I think we're proceeding on the assumption that the bombers are still at large, and of course that adds a special urgency to figuring out who's done this," Chertoff said on the ABC television program "This Week." Four blasts tore through London's transport network on Thursday, killing more than 50 people on three subway trains and a double-decker bus. Chertoff said it was too early to conclude that no suicide bombers had been involved. Police in London said the subway bombs went off almost simultaneously, making it more likely they were detonated by timers rather than suicide bombers. --More 2240 Local Time 1940 GMT
