A U.S.-trained Al Qaeda microbiologist has been released from jail by the Malaysian government, prompting alarm among American counterterrorism officials.

"This individual is considered dangerous," said one official, referring to the recent decision to free Yazid Sufaat, a notorious Qaeda operative who once oversaw the group's germ-warfare efforts. The official declined to be identified talking about sensitive information.

Safaat had been in Malaysian custody since December 2001, when he was arrested because of his alleged involvement with Jemaah Islamiah, a radical South Asian terror group closely linked with Al Qaeda. But two weeks ago, Malaysia's interior minister, Datuk Seri Syed Hamid Albar, announced that Sufaat and five other detained Islamic militants were being freed because "they are no longer a threat and will no longer pose a threat to public order." Albar added that Sufaat "has been rehabilitated and can return to society."

Malaysia privately informed the Bush administration that its legal authority to detain Sufaat had expired but promised Washington that he would be kept under close observation, the U.S. official indicated. But counterterror officials here expressed doubt that Sufaat has abandoned his radical Qaeda views or his desire to attack the United States with biological weapons. They also point out that Sufaat played an assisting role in planning the 9/11 attacks. He hosted two of the hijackers along with two other veteran Al Qaeda operatives at a terror "summit" in Kuala Lumpur in January 2000.

The timing of Sufaat's release was especially awkward for U.S. officials. The Qaeda scientist was freed on Dec. 4—the day after a congressionally mandated commission on weapons of mass destruction released a public report warning of the risk of a biological weapons attack in the next five years.

"There's a troubling irony that this happened the day after our report," said Bob Graham, the former Florida senator and chairman of the Senate Intelligence Committee, who served as co-chairman of the bioweapons panel. (In an interview with NEWSWEEK the day the report was released, Graham said he was particularly concerned about "the degree of risk associated with a biological weapon … The ubiquitous nature of pathogens and the increasing lethality of both natural and synthetic pathogens led our commission to conclude it's more likely that an attack will come biologically rather than nuclear.")