Germany Says It Foiled Bomb Plot

One of the skills taught in these camps, intelligence officials say, is how to make peroxide-based explosives, which can be assembled from materials available at drugstores and are difficult for police to detect.

The most commonly used compound is triacetone triperoxide, or TATP, which can be made from household products such as nail polish remover and hydrogen peroxide by concentrating the solutions and mixing them with other ingredients. The resulting compound is highly unstable and can detonate at any time.

British investigators have said that TATP and a related compound, HMTD, hexamethylene triperoxide diamine, were the primary explosives in the London transit attacks and in the disrupted August 2006 plot to blow up several airliners flying from Britain to the United States. British citizen Richard Reid tried unsuccessfully to use a TATP bomb concealed in his shoe to blow up an American Airlines jet en route from Paris to Miami in 2001.

German officials said Wednesday that one of the suspects seized Tuesday had been detained briefly by German police in December after he was seen acting suspiciously outside a U.S. military installation in Hanau. He was quickly released without charge.

Investigators and other sources said tracking of the cell began in earnest this spring when U.S. officials tipped off their German counterparts about the suspects' travels between Pakistan and Germany, as well as their affiliation with Islamic Jihad Union, a group with no previously known presence in Europe.

The group is an offshoot of the Islamic Movement of Uzbekistan, which has been branded a terrorist organization by the U.S. government. Based in Central Asia, it asserted responsibility for suicide bombings in the Uzbek capital, Tashkent, in July 2004 near the U.S. and Israeli embassies.

Uzbek militants have become prominent in recent years along the border between Afghanistan and Pakistan, and counterterrorism analysts said they sometimes cooperate with al-Qaeda and Taliban fighters.

In mid-spring, German authorities informed the Americans that cell members had obtained a house in Hanau, according to a senior U.S. intelligence official, who spoke on condition of anonymity.

The cell's activities prompted the U.S. Embassy in Berlin to issue a warning April 20 of an increased threat of terrorism in Germany, particularly against Americans. Officials did not elaborate on the nature of the threat at the time.

Since then, information flowed regularly between U.S. and German intelligence officials. The U.S. contribution was mostly electronic intercepts, while the Germans handled operations on the ground, the official said. "They employed a lot of people operating in several areas of their country," he added.

German prosecutors said that in February, the suspects started acquiring liquid hydrogen peroxide, ultimately amassing 1,600 pounds of it. Investigators said the cell purchased the chemicals from stores near Hanover, in central Germany, but stored them in a different part of the country -- in a garage in Freudenstadt, a town in the Black Forest in the southwest.

In July, authorities managed to swap out the chemicals.