Sixteen rocket warheads found last week in south-central Iraq by Polish troops did not contain deadly chemicals, a coalition spokesman said yesterday, but U.S. and Polish officials agreed that insurgents loyal to former Iraqi president Saddam Hussein and foreign terrorist fighters are trying to buy such old weapons or purchase the services of Iraqi scientists who know how to make them.

The Coalition Press Information Center in Baghdad said in a statement yesterday that the 122-milimeter rocket rounds, which initially showed traces of sarin, "were all empty and tested negative for any type of chemicals." The statement came just hours after two senior Polish defense officials told reporters in Warsaw, based on preliminary reports, that the rocket rounds contained deadly sarin and that actions by the Polish unit in Iraq kept them from being purchased by militants fighting coalition forces.

Yesterday's coalition release also said that two other 122-milimeter rounds, found by the Poles on June 16 with help from an Iraqi informer, tested positive for small quantities of sarin but were "so deteriorated" that they would have had "limited to no impact if used by insurgents against coalition forces."

The Poles' discoveries generated renewed talk that prewar claims about Hussein's stock of unconventional weapons might yet prove true. Defense Secretary Donald H. Rumsfeld, for example, told an interviewer on Wednesday that the Polish defense minister, Jerzy Szmajdzinski, told him about the weapons last weekend at the NATO meeting in Turkey. Though Rumsfeld made it clear he had no personal knowledge of test results, he said that the Poles "believe that they are correct that these, in fact, were undeclared chemical weapons -- sarin and mustard gas."

Szmajdzinski told Polish radio that the rockets and mortars had probably been hidden from United Nations inspectors. "Our predictions and reports that Saddam Hussein did not come clean with a large sum of weapons, artillery shells and of weapons of mass destruction were proven true," he said. "Some of those warheads were old, but it could not be ruled out some could still be used."

Charles Duelfer, the chief U.S. weapons inspector in Iraq, told Fox News on June 24 that "some" old sarin and mustard rounds have been discovered in scattered places, demonstrating "that the Iraqi declarations were wrong at least in . . . amount." But Duelfer cautioned he was not ready to make any judgment whether there were any "still concealed" military-capable stockpiles.

Duelfer said the current danger he sees is that some anti-coalition forces and foreign terrorist groups are trying to tap into Iraq's weapons expertise for use against the United States. "Former experts in [Hussein's] weapons-of-mass-destruction program," he said, "are being recruited by anti-coalition groups." As a result, he said, his Iraqi Survey Group (ISG) is "keeping a very close eye on some anti-regime people."

In Warsaw yesterday, Marek Dukaczewski, Poland's chief of army intelligence, told reporters: "We were mortified by the information that terrorists were looking for these warheads. . . . An attack with such weapons would be hard to imagine."

Dukaczewski said the Polish unit in Iraq paid an undisclosed sum of money to buy the rockets last month after an informer there told the Poles that militant groups were seeking to buy such weapons for up to $5,000 apiece. "We bought all the shells available," Dukaczewski said.

In Washington yesterday, a senior intelligence official said he was unaware that the Poles purchased rather than found the weapons. He said the United States had been told they were discovered at several sites, mixed in with conventional 122-milimeter rockets and without any distinctive markings.

Duelfer, who as CIA Director George J. Tenet's personal representative directs the ISG's weapons search, told Fox News that the rocket rounds were found in former depots but that so far "we're not able to establish how these rounds got to where we found them" or "who had custody of them, if anyone."

In January 2003, U.N. inspectors discovered a dozen old 122-milimeter rockets that chief inspector Hans Blix described at the time as "designed to carry chemical weapons." Iraq later turned up several more, and all were destroyed. Blix later said he was not sure whether Iraq mentioned them in the 12,000-page weapons declaration it submitted in December 2002.

Correspondent Craig Whitlock in Berlin contributed to this report.