The U.N. weapons inspections team more than doubled in size Sunday with the arrival of reinforcements to speed up the probe into Iraq's possible nuclear, chemical and biological weapons programs.

As the 25 new inspectors arrived, U.N. monitors who have been on the ground for two weeks went about their daily rounds — including a surprise visit to the State Company for Geological Survey and Mining here in the capital, Baghdad.

A nuclear team spent about two hours in the two-building complex, which in the past was involved in uranium processes that could help prepare fuel for nuclear bombs.

Earlier Sunday at the Baghdad airport, the first of eight helicopters destined for the U.N. operation was being assembled after being flown in as cargo a day earlier. With the helicopters, arms monitors can range farther afield on their surprise inspections.

Searches began in late November when two dozen inspectors arrived to resume the U.N. arms monitoring program after a four-year break. In the 1990s, under post-Gulf War U.N. resolutions, inspectors destroyed large amounts of Iraqi chemical and biological weapons, and dismantled Iraq's program for building nuclear bombs.

Those inspections collapsed in 1998 amid U.N.-Iraqi disputes over access to sites and over U.S. spies within the U.N. operation.

The new team operates under a U.N. Security Council mandate requiring Iraq to surrender any remaining weapons of mass destruction and shut down related programs.

Meeting one part of that resolution, Iraq turned over a declaration of its weapons programs before Sunday's deadline. Computer disks and about 12,000 pages of documents were flown to U.N. headquarters in New York and the International Atomic Energy Agency headquarters in Vienna, Austria.

The new inspectors are 21 nuclear experts from the atomic agency, and four specialists from the U.N. Monitoring, Verification and Inspection Commission (UNMOVIC), U.N. spokesman Hiro Ueki said.

Ueki, who arrived with the inspectors from a U.N. base in Cyprus, said 20 to 30 more inspectors, most of them from UNMOVIC, were to arrive Tuesday.

By the end of December, 80 to 100 U.N. experts will be making daily inspections in Iraq, U.N. officials say.

Monitors on Sunday refused to comment about their duties, as usual, to journalists waiting outside inspection sites. But Iraqi officials at the State Company for Geological Survey and Mining invited in reporters after the inspectors left.

The company's chief geologist, Moussa Jaafar al-Attiyah, called it "an ordinary visit," similar to 10 U.N. inspections of the site in the 1990s. Asked whether he found the inspection humiliating, as some Iraqis have suggested, al-Attiyah said: "You are right. This is not a welcome visit."

Al-Attiyah, who has worked at the site for 35 years, said the inspectors asked to check offices and laboratories. He said they looked for equipment inventoried and tagged by their predecessors in the 1990s, to ensure they were not moved.

Another inspection team, including chemical specialists, visited a pesticide plant outside Falluja, 30 miles west of Baghdad. Pesticide-making equipment and components can be used to produce chemical weapons.

So far, the U.N. teams have largely revisited sites inspected by their predecessors in the 1990s to ensure that equipment is where it should be and that no banned items were being produced.