Advanced bombs were so powerful that none of dead have been identified

LONDON — Al Qaida employed light but advanced bombs detonated by timers in last week’s bloody strike on London’s mass transit system.

Officials said the bombs were so powerful that none of the 49 known dead had been identified over the weekend. They said the four bombs were detonated within 50 seconds.

British officials said authorities have determined that the four bombs that blew up in subways and a bus in London on July 7 were composed of less than 4.5 kilograms of explosives each. They said the bombs were small enough to fit in a knapsack and were detonated by timers rather than suicide attackers.

[On late Saturday, British authorities evacuated the downtown section of Birmingham amid an alert of an impending insurgency attack, Middle East Newsline reported. The evacuation took place amid a jazz festival attended by tens of thousands of people.]

“All we are saying is that it is high explosives,” Scotland Yard Deputy Assistant Commissioner Brian Paddick told a news conference on Saturday.

“That would tend to suggest that it is not home-made explosive. Whether it is military explosive, whether it is commercial explosive, whether it is plastic explosive we do not want to say at this stage.”

At least 49 people were killed and another 700 were injured in the London bombings, but officials said they expected the casualty toll to rise.

On Saturday, a second Al Qaida group, entitled Abu Hafs Al Masri Brigade, claimed responsibility for the attacks.

“It would appear now that all three bombs on the London Underground system actually exploded within seconds of each other,” Paddick said. “In fact, the three bombs exploded almost simultaneously.”

Officials said the bombs were placed on the floor of three subway cars.

The fourth bomb was placed either on the floor or on a seat of a double-decker bus.

“Initially, the forensic investigation suggests that each device used had less than 10 pounds of high explosives,” Assistant Police Commissioner Andy Hayman said.

Officials said the bombs were much smaller than those used in Islamic insurgency attacks in Egypt, Iraq and Israel. Many of those attacks were conducted by suicide operatives with bombs of 10 or more kilograms.

British authorities have sought to question Mohammed Garbazi, a cleric sentenced by a Moroccan court to 20 years on charges of being linked to Al Qaida suicide attacks in Casablanca in which 45 people were killed in 2003.

Garbazi was also suspected of being connected to the Madrid train bombings in March 2004.

Officials said they could not rule out the prospect that cellular phones were used to detonate the London bombings. Cell phones were used to explode the bombs in Madrid.

“As far as the general threat assessment was concerned, we didn’t have prior knowledge of this attack,” British Home Secretary Charles Clarke told the Sky News network. “We obviously are looking very carefully at all our intelligence to see if anything was missed, but in fact we don’t believe anything was missed. It just came out of the blue.”

Officials said the investigation and search for bodies have been hampered by the fear of a subway tunnel collapse. They said authorities hope to acquire more information by viewing the closed-circuit television cameras, or CCTV, installed throughout the London subway system.

“If they weren’t suicide bombers, then they must have got on and off these trains,” Andy Trotter, deputy chief constable of the British Transport Police, said. “That means their pictures can be grabbed from CCTV cameras.

The Underground network is a CCTV-rich environment, and so this is going to be an intense investigation to look at the images.”