UN arms experts have questioned Iraqi scientists at a Baghdad college and visited at least two other suspect sites.
Iraqi officials said senior inspectors from the International Atomic Energy Agency (IAEA) and U.N. Monitoring, Verification and Inspection Commission (UNMOVIC) had visited the Technology University in the capital on Thursday and questioned the heads of departments and the dean of the facility.
They also checked equipment tagged by previous inspection teams at a laboratory of the chemical engineering department.
The dean, Mazen Joumaah, told reporters the inspectors were "highly professional and knew what they wanted". He said they had asked his staff for precise details of the higher education curriculum in various subjects at the college.
IAEA experts had interviewed a senior nuclear scientist at the college on Tuesday who was a member of Iraq's past nuclear programme. That interview marked the formal resumption of a regular interview programme suspended in 1998.
Other UNMOVIC teams went to Yousifiyah, 20 km (12 miles) south of Baghdad, and were inspecting an oil products facility and a military industrial plant, the Iraqi officials said.
UNMOVIC and IAEA experts inspected seven sites on Wednesday, declining to take a break for Christmas. With their mission in its fifth week, the inspectors have now completed more than 170 missions, visiting many sites more than once.
The inspectors returned to Iraq last month after a four-year hiatus to resume a hunt for weapons of mass destruction, amid threats by the United States to disarm Iraq by force if it does not obey U.N. resolutions.