Empty warheads 'not a smoking gun' - but tests may yet show nerve gas traces

The big question over yesterday's find of empty chemical warheads at an Iraqi ammunition storage area is whether the warheads contain traces of the nerve agent VX, the deadliest chemical weapon in Iraq's banned arsenal.

If traces of VX – or any other chemical agent, such as mustard gas – were found on any of the warheads, it would be a clear contradiction of Iraq's claim that it no longer holds any weapons of mass destruction.

If the chief weapons inspector, Hans Blix, determines that Iraq is in breach of its disarmament obligations, he is duty-bound to go straight to the UN Security Council to report the violation.

The UN spokesman in Baghdad, Hiro Ueki, said that one of the dozen empty 122mm chemical warheads discovered during an inspection of an ammunition storage area required "further evaluation." But he also said that the UN did not consider the find to be a "smoking gun."

As of last night, it was not clear whether the warheads were some that had previously been accounted for by the weapons inspectors. Last month they secured a dozen artillery shells filled with mustard gas, which had been itemised by the former UN weapons regime. But since the weekend, apparently acting on fresh intelligence, the 100 or so weapons inspectors in Iraq have stepped up their work and are acting much more aggressively.

Mr Ueki said the missiles were similar to ones imported by Iraq during the late 1980s. The UN team, which was inspecting bunkers built in the late 1990s at the Ukhaider ammunition storage area, used portable X-ray equipment to conduct a preliminary analysis of one of the warheads, and collected samples for chemical testing.

The inspectors are back in familiar territory: in 1997, they discovered warhead remnants with traces of VX on them. After weeks of wrangling, President Saddam Hussein agreed to tests in the United States, but when the results came out positive, the Iraqi government accused the US of deliberately contaminating the tests.

The inspectors then agreed to send the remnants for further testing in France and Switzerland, but amid high political tensions the matter was not fully resolved before the weapons monitors pulled out of Iraq in December 1998.

The inspectors have complained that the 12,000 pages of Iraq's "full, final and complete" report on its weapons of mass destruction issued on 7 December contained very little new information. Iraq has been warned by the US that its lack of candour constitutes a "material breach" – a code word that can be used to trigger a war.

Until now, the rest of the UN Security Council has not gone along with the US view. Tony Blair suggested on Monday that it might only be a matter of a short time before a "smoking gun" would appear that will convince the other 14 Council members that Iraq is back to its old tricks.