US forces have detained a top female scientist involved in Iraq's biological warfare programs, Huda Salih Mahdi Ammash, a US-trained microbiologist dubbed "Mrs Anthrax."

Ammash, 49, was the only woman on the US list of the 55 most wanted Iraqis headed by Saddam Hussein. But the United States considers it a major catch as it steps up the hunt for evidence of he banned nuclear, biological and chemical weapons it accuses Baghdad of developing.

Fifty-third on the list, Ammash was the five of hearts in the deck of US playing cards featuring the wanted Iraqis, and was described as a "weapons of mass destruction scientist."

"This would be very important to the coalition in their ability to get additional information about the scope of the (biological warfare) program," a US official said, speaking on condition of anonymity.

US forces in Iraq have yet to discover any weapons of mass destruction -- the primary justification for the US-led invasion that toppled the regime of Saddam Hussein.

"We're going to find what we find as a result of talking to people, I believe, not simply by going to some site and hoping to discover it," US Defense Secretary Donald Rumsfeld said in a television interview Sunday.

Ammash, dubbed "Mrs Anthrax" by the tabloid press, surfaced in a video recording of Saddam meeting top advisers aired shortly after the start of the US-led war against Iraq March 20.

She was appointed to Iraq's ruling Baath Party's regional command in 2001 and is believed to have been a leader of its biological warfare program. Ammash shares the distinction with another woman, Rihab Taha, known as "Dr Germ," who is still at large.

A senior US defense official said Ammash was taken into US military custody on Sunday in Iraq.

"She's on the list of 55 because has information of potential value on the extent and depth of the weapons of mass destruction program, as well as on the specifics of those programs," he said.

Another US official said Ammash was "a leading figure in Iraq's microbial genetic engineering."

Born in Baghdad in 1953, she did graduate studies in microbiology in the United States, receiving a master's degree from the University of Texas College of Women in 1979, and a doctorate from the University of Missouri in 1983.

She was a professor of microbiology at Baghdad University and dean of the College of Science.

Ammash would be the 19th Iraqi on the wanted list to be detained if US authorities confirm the capture of Mizban Khidir Hadi, whose capture was reported Saturday by the Washington Post.