LYON, France -- Menad Benchellali, thin and bearded, was known among his Arab friends as "the chemist" because of the special skills he learned at al Qaeda training camps in Afghanistan. When he returned to his native France in 2001, according to investigators, he set up a laboratory in his parents' spare bedroom and began to manufacture ricin, one of the deadliest known substances.

Working at night with windows open to dissipate fumes from the process, he blended ingredients in a coffee decanter and spooned the doughy mixture onto newspapers to dry. The final product was a white power that Benchellali stored in small glass flasks and old jars of Nivea skin cream -- to be used, as he later told police, "in the event I became involved in the jihad."

Today, exactly how many jars of ricin the 29-year-old Benchellali may have produced -- and their whereabouts -- is an urgent question for European governments facing a wave of terrorist attacks and threats. Last year, investigators say, similar containers turned up in Britain, in the possession of North Africans who were allegedly planning an attack. At least one other jar is known to be missing, and French investigators suspect that still others exist.

The story of Benchellali's laboratory offers a glimpse into a secret world of suspected terrorists and their quest for biological and chemical weapons. According to European investigators, a string of incidents in recent months points to a particular interest in ricin, the highly lethal toxin that comes from castor beans. Other powerful poisons that also are relatively easy to obtain and use -- botulinum toxin and industrial chemicals such as potassium cyanide and osmium tetroxide -- have also been sought by suspected terrorists. In April, police in Jordan foiled what government officials said was a plot to use chemical bombs and poison gas in a series of attacks on embassies and government buildings in Amman, the capital.

So far, no poison attacks by al Qaeda-related groups have been carried out, and many experts say they believe that terrorist groups still haven't mastered the skills needed to make an effective weapon. But they clearly are trying. Lacking facilities for making advanced chemical or biological arms, investigators say these groups are seeking toxins that can be easily bought, stolen or manufactured in an ordinary kitchen using common ingredients...