London Bombers Used Simple Stuff

The London suicide bombers cooked up their explosives using mundane items, such as hydrogen peroxide. They stored them in a fancy commercial refrigerator that was out of place in their grimy apartment. And cellphones were probably used to set the bombs off.

Those details from the July 7 London bombing emerged Wednesday at a wide-ranging briefing given by the New York Police Department to city business leaders.

The unusual briefing -- based partly on information NYPD detectives learned when they went to London to monitor the investigation -- was part of a program designed to encourage more vigilance by private security at large hotels, Wall Street firms, storage facilities and other companies.

Police Commissioner Raymond W. Kelly warned that the materials and methods used in the London attack were easily adaptable to New York.

“Initially it was thought that perhaps the materials were high-end military explosives that were smuggled, but it turns out not to be the case,” Kelly said. “It’s more like these terrorists went to a hardware store or some beauty supply store.”

The NYPD officials said investigators thought the bombers used a peroxide-based explosive called HMDT, or hexamethylene triperoxide diamine. HMDT can be made using ordinary ingredients such as hydrogen peroxide (hair bleach), citric acid (a common food preservative) and heat tablets (sometimes used by the military for cooking).

HMDT degrades at room temperature, so the bombers preserved it in a way that should have been an early warning sign, said Michael Sheehan, deputy commissioner of counter-terrorism at the nation’s largest police department.

“In the flophouse where this was built in Leeds, they had commercial-grade refrigerators to keep the materials cool,” Sheehan said, describing the setup as “an indicator of a problem.”

Among other details cited by NYPD officials:

* The bombers transported the explosives to the outskirts of London in beverage coolers tucked in the back of two cars.

* Investigators believed the three bombs that exploded in the subway were detonated by cellphones that had alarms set to 8:50 a.m.

* Similar explosive compounds were used in the attempted attack in London on July 21. However, the detonators were hand-activated, not timed.

Sheehan said the NYPD was troubled by information it had received about the bombers’ links to certain organizations, but he did not name any groups.

“We know those same types of organizations that they’re affiliated with are very much present in New York City,” he said. “That’s something we’re studying very, very carefully.... This could happen here.”

After the briefing, police spokesman Paul Browne said the department had clearance from British authorities to present information about the July 7 attack, which killed 52 people and the four bombers.

The session at police headquarters in Lower Manhattan was attended by officials from police departments and law enforcement agencies in Baltimore, Washington, Philadelphia and other jurisdictions. The officials were in the city discussing plans to beef up security along Amtrak’s New York-Washington route.