Al-Dawrah, Iraq ? The U.N. weapons hunters, sweeping Thursday through a disused bio-warfare installation, spotted a disconnected refrigerator. They moved in, threw open the door and recoiled in disgust.

The stench may have come from a batch of harmless material left from a long-ago veterinary experiment. But it got the full treatment – a swab, a sample, analysis to come – in the second day of the painstaking U.N. search for any Iraqi doomsday arms.

After a four-year break, the international experts revisited two sites from Iraq’s old weapons programs: a high-tech machining operation that could be key to any nuclear bomb-building, and a veterinary vaccine plant where deadly biological weapons were concocted a decade ago.

They found open doors.

“It’s a good start for the inspections,” said Jacques Baute, team leader for the nuclear experts.

The work inspectors do in the months to come – to eliminate any Iraqi weapons of mass destruction, or at least to reduce the possibility of them – must be convincing enough to avert a U.S. call for international military action to disarm the Baghdad government. From Iraq’s point of view, the inspections must be good enough to persuade the Security Council to lift the U.N. economic sanctions crippling its economy.

But first the arms monitors must make a dent in a list of sites potentially connected with programs to produce weapons. They have begun by returning to important facilities surveyed and “neutralized” by U.N. inspectors in the 1990s.

The experts believe Iraq may retain some weapons, including some of the tons of botulinum toxin – a deadly biological agent – produced at al-Dawrah before the Gulf War. This is “part of what we call unresolved issues,” said Demetrius Perricos, in command of the chemical-biological inspectors in Iraq.