Hexogen is one of the most powerful conventional explosives. Developed during World War II, it is a hard, white solid that is relatively safe and inexpensive. It is usually mixed with oils or waxes to make a plastic explosive.

Considered more effective than TNT, it is primarily a military explosive with a few specialty applications in the oil industry.

Following are terror-related cases where hexogen was discovered:

• August 2004: Russian authorities report finding traces of the explosive hexogen in the wreckage of two airliners that crashed nearly simultaneously, killing 90 people.

• August 2000: Bomb blasts at a popular shopping center in Riga, Latvia, injures 28 people, three seriously. Police officials report hexogen may have been used.

• November 1999: St. Petersburg police arrest a man found with four sections of a missile warhead carrying high explosives. Itar-Tass said the segments contained hexogen.

• September 1999: Moscow apartment bombings kill some 300 people. Authorities blame Chechen separatists for the explosions, which involved hexogen.

• February 1985: West German police arrest a man at Frankfurt Airport after finding his luggage contained 10 kilograms of explosives identified as hexogen.

• October 1983: In Beirut, Lebanon, a suicide bomber rams a truck packed with explosives into U.S. Marine headquarters, killing 241 U.S. servicemen.