Dr. Rihab Rashid Taha, a scientist who helped Iraq make weapons out of anthrax, surrendered over the weekend, said Maj. Brad Lowell of the U.S. Central Command in Tampa, Fla. 

Also in custody Monday was Ibrahim Ahmad Abd al Sattar Muhammad, armed forces chief of staff since 1999, Pentagon officials said without giving details of his capture. 

He was No. 11 on a list issued last month of the 55 most wanted former members of Saddam's government, the jack of spades in a card deck issued to troops. 

The two could know much about any unconventional weapons the government had, but it was far from certain what kind of information they would divulge to American interrogators. Other former senior leaders have largely denied under questioning that the country had programs for biological, nuclear or chemical weapons - the Bush administration rationale for waging the war. 

Nearly two dozen of the top 55 are in custody, officials said. 

U.N. weapons inspectors nicknamed Taha "Dr. Germ" because she ran the Iraqi biological weapons facility where scientists worked with anthrax, botulinum toxin and aflatoxin. A microbiologist, Taha holds a doctorate from the University of East Anglia in Britain. 

U.N. inspectors who searched Iraq for weapons of mass destruction in the 1990s paid Taha the dubious honor of making her one of the few Iraqis singled out by name in their final report. They said Taha's 1985 transfer from Baghdad University to an anthrax research site at the government's Al-Muthanna complex was linked to a resurgence of Iraq's research into biological weapons. 

Taha is not on the list of the 55 most wanted, but among 200 Iraqis that Defense Secretary Donald H. Rumsfeld has said are sought but who he did not publicly identify. 

In a February interview with the British Broadcasting Corp., Taha said she "played a major role in Iraq's biological weapons program in the 1980s and 90s, but it was only for self-defense and not for use." 

American forces had been trying to capture her and last month raided her Baghdad home, carrying away boxes of documents but not finding her or her husband. 

Taha is married to Amer Rashid, who held top posts in Saddam's missile programs and was oil minister before the war. Rashid surrendered to U.S. forces April 28, 12 days after that Baghdad raid, and Taha had been negotiating her surrender over an undisclosed period, officials said Monday. 

Rashid is the six of spades in the deck of cards. The couple married in 1994 and has a young daughter. 

Current and former inspectors who interviewed Taha in the mid-1990s described her as difficult and dour, and press reports said she once broke a chair in anger during U.N. questioning. 

The Iraqis presented her as the head of the biological program, but inspectors suspected she may have been fronting for someone more senior. 

Officials have captured a number of other former officials who they had hoped would give information on the unconventional weapons programs. Last week they reported the capture of Huda Salih Mahdi Ammash, along with Taha one of the rare women among Saddam's circle. Ammash was among the 55 most wanted and a woman officials believe played a key role in rebuilding Baghdad's biological weapons capability in the 1990s. 

Although the U.S.-led military coalition that defeated Saddam's army in April has mounted an extensive search for the suspected unconventional weapons, no weapons stockpile has been found. 

Chief U.N. weapons inspector Hans Blix said last month that Taha and her husband would be among "the most interesting persons" for the Americans to question. Blix's teams pulled out of Iraq shortly before the war began after 3 1/2 months work. 

In the February interview with BBC, Taha said she was involved in producing Iraq's final weapons declaration to the United Nations. She said Saddam's government was telling the truth when it said it no longer had any chemical or biological weapons. 

Taha told the BBC her country never planned to use the biological agents it produced in the 1980s and early 1990s. 

"We never wanted to cause harm or damage to anybody," she said. "Iraq has been threatened by different enemies and we are in an area that suffers from regional conflict. I think it is our right to have something to defend ourselves and to have something as a deterrent."