Dr Taha: Educated in England
The White House says President George W Bush is pleased with the arrests that have been made since the end of the war in Iraq.
The latest to surrender was a senior scientist who worked on Saddam Hussein's bacterial weapons programme, Rihab Rashid Taha, who was nicknamed Doctor Germ.
She was not on the list of the most wanted former Iraqi leaders, but American officials hope she can help them locate banned weapons of mass destruction.
The announcement of Dr Rashid Taha's came as a new US administrator, Paul Bremer, arrived in Baghdad as part of a major shake-up of the American post-war team.
Major Brad Lowell at US Central Command in Qatar said Dr Rashid Taha had been negotiating her surrender for days, and that she had turned herself in during the last 48 hours.
US forces had been searching for her and unsuccessfully raided her Baghdad home in April, hoping to capture her and her husband.
She is married to General Amir Mohammad Rashid, the former Iraqi Oil Minister, who surrendered to US forces on 28 April - 12 days after that raid. He previously held top posts in Iraq's missile programmes.
The UN chief weapons inspector, Hans Blix, recently said they would be among the most interesting people to question about weapons development.
The United States suspects that Saddam Hussein's regime kept large stocks of biological and chemical weapons, and cited these arms as justification for launching the invasion of Iraq.
But no such stocks have been found yet and the Washington Post reports that the US is scaling down its team of weapons experts in Iraq.
A microbiologist, Dr Taha holds a doctorate from the UK's University of East Anglia, where she studied plant disease.
She is said to have carried out work on germs that cause botulism poisoning and anthrax infections at the top-secret biological research lab al-Hakim in the late 1980s.
At that time, she was reported to have ordered, and received, biological specimens from US companies.
Weapons inspectors who met her in the mid-1990s described her as difficult and dour.
She admitted producing germ warfare agents in the past, including anthrax and botulinum, but said they were later destroyed, Reuters reports.
Last week, coalition forces announced the capture of Huda Salih Mahdi Ammash, dubbed "Mrs Anthrax" - another woman believed to have played a key role in developing Iraq's biological weapons capability.
US officials say 20 of the 55 most wanted Iraqis are now in custody - another three are dead.
US forces have discovered a second suspected mobile laboratory which they say might have been used to produce biological weapons.
The trailer was found near the northern city of Mosul and is similar to one found in northern Iraq earlier this month.
The US-run Information Radio in Iraq has announced unspecified rewards for Iraqis who provide information leading to the discovery any of the suspected weapons of mass destruction.