A newly reinforced corps of U.N. weapons monitors, rapidly expanding its schedule of surprise inspections, sent teams out across the Iraqi countryside again Wednesday and made return visits to a large complex where Iraq once worked on a nuclear bomb.

Deep in the western Iraqi desert, near the Syrian border, another U.N. team was in the second day of its inspection of a remote uranium mining site.

It was the start of the third week of inspections, after a four-year gap, under a new U.N. Security Council resolution mandating that Iraq surrender any weapons of mass destruction and report on nuclear, biological and chemical research and production.

That report, totaling 12,000 pages, was filed over the weekend and was already being scrutinized closely for any new sources of concern about the Iraqi arsenal and intentions.

The five permanent members of the U.N. Security Council — the United States, Russia, Britain, France and China — were given uncensored copies of the report. Copies given to the other 10 council members will have sensitive details of nuclear technology edited out, a move that some of the countries saw as an affront.

On Tuesday, U.N. Secretary-General Kofi Annan said that decision was "fine, but the approach and style were wrong."

Such new information would aid in planning the arms monitors' work in Iraq over the coming months. U.N. officials hope to cover hundreds of industrial and research installations, many of them "dual-use" sites whose products or equipment could be devoted to either civilian or military use.

Twenty-eight new inspectors flew to Baghdad on Tuesday, bolstering the U.N. operation to 70 inspectors. U.N. technicians also readied the first of eight helicopters expected to join the monitoring effort.

The United Nations hopes to have 80 to 100 inspectors at work in the field each day by late December. They come from both the Vienna-based International Atomic Energy Agency and the U.N. Monitoring, Verification and Inspection Commission, UNMOVIC, whose inspectors specialize in chemical and biological weapons and missiles.

On Tuesday, they mounted the largest number of inspections yet, visiting 13 sites. The farthest afield was the al-Qaim mining operation at Akashat, in the desert 250 miles west of the Iraqi capital. That inspection was scheduled to last two to three days.

In the 1980s, the Iraqis exploited the phosphate deposits at al-Qaim for their uranium content as well as for fertilizer, producing some 100 tons of uranium over six years. The site came under U.N. inspections during a previous monitoring regime in the 1990s.

An UNMOVIC statement said the al-Qaim team "is tasked with verifying the status of destroyed equipment [and] to determine that no uranium extraction activities have been resumed."

Other nuclear inspectors Wednesday again visited al-Tuwaitha, Iraq's major nuclear research center, 15 miles southeast of Baghdad. In the 1980s, Iraqi scientists and engineers at al-Tuwaitha worked on developing technology for enriching uranium to levels usable in bombs.

The complex contains more than 100 buildings, many of which were destroyed in U.S. bombing during the 1991 Gulf War. U.N. officials said the new round of inspections there would last at least through Thursday, as IAEA specialists checked for any signs of revived Iraqi interest in nuclear weaponry.

The U.N. inspections of the 1990s, after Iraq's defeat in the Gulf War, led to the destruction of tons of Iraqi chemical and biological weapons, and to the dismantlement of Iraq's program to try to build atomic bombs. That monitoring regime broke down in 1998 amid U.N.-Iraqi disputes.

If the monitors ultimately report full Iraqi cooperation with the U.N. disarmament demands, U.N. resolutions call for the Security Council to consider lifting economic sanctions imposed on Iraq after it invaded Kuwait in 1990. If, on the other hand, Iraq is found in noncompliance, the council may consider military action against Iraq.

President Bush has threatened military action in that case even without U.N. authority.