Summary Although the kind of bombs used in the July 7 attacks on London underground rail system and on a double-decker bus is unclear, there are several possibilities. Analysis At approximately 8:50 a.m. local time July 7, an explosion was reported at the Liverpool Street underground train station in London. By 9:05 a.m. local time, blasts also had been reported near that Aldgate East, Edgware Road, King's Cross, Moorgate and Russell Square tube stations. More than an hour later, an explosion reportedly occurred on a double-decker bus at Tavistock Square. At least 45 people have been reported killed in the blasts, according to Britain's Skynews, and another 1,000 or more have been injured. The location of the blasts indicates that at least three devices exploded underground, one near the Aldgate East station on the Circle and District line and all others west of the first. All but one blast apparently occurred on the Circle line. Furthermore, the blast on the double-decker bus has been confirmed. The kind of devices used in these explosions is unclear, although the possibilities include command-detonated suicide bombers, command-detonated improvised explosive devices or timed explosive devices. Because all of the blasts occurred at nearly the same time on separate underground lines, it would have been nearly impossible for a single individual to have planted all of the devices on each train -- meaning several bombers were involved in this operation. It also is possible that someone planted timed explosives on the trains, knowing the general time needed to travel between stations, so the devices were set to detonate upon arrival at the next train station. If the devices were command-detonated, the use of a cellular telephone to trigger the devices is unlikely, since cellular phones typically do not work inside the tube system. There are sporadic reports that several of the bombs exploded while pulling into stations. The attackers could have used command-detonated bombs to allow for a more precise detonation time and increased casualties while in the station -- rather than planting timed devices inside the trains that could go off at the wrong time if the train was delayed even slightly. If the bombers are following the Madrid model, they left timed devices inside the trains -- in order to live to attack another day.