When the Food and Drug Administration temporarily suspended imports of fruit from Chile 18 months ago after the discovery that two grapes had been spiked with cyanide, it brought down the wrath of the Chilean government.

The FDA, Chile said, bungled the investigation. Hinting at a broad U.S. conspiracy, the Chileans claimed to have scientific evidence that the cyanide detected in the two suspect grapes was put there by the FDA. Sen. Jesse Helms (R-N.C.), acting on the Chilean government's behalf, ordered a federal investigation of the agency's conduct.

The investigation, which was completed by the General Accounting Office this summer, has not been released by Helm's office. But a copy of the report, which was obtained by The Washington Post, shows that there may be a good deal less to the controversy than meets the eye.

"We found that FDA's discovery of cyanide in Chilean grapes was based on generally accepted tests that were conducted properly," the GAO said. "Based on its finding, FDA acted within its legal authority to suspend imports of Chilean fruit . . . . "

The controversy over the grapes, which the Chilean government claims cost its country in excess of $300 million in lost sales, centers on the conclusion reached by a FDA laboratory that two grapes taken from a shipment of Chilean fruit at the port of Philadelphia were contaminated with cyanide.

The Chilean government argued that the agency used the wrong tests to look for cyanide, violated standard operating procedures for conducting lab analyses and did not exercise adequate control to protect the samples from inadvertent contamination.

In addition, Chilean-sponsored scientists said that because of the speed at which cyanide dissipates, there should have been no cyanide left for the FDA to detect if, as the agency contended, the grapes had been poisoned in Chile. The allegedly poisoned grapes, they said, would also have been dried out by the poison after two weeks on a boat, and not have been plump and healthy looking like the grapes seized by the FDA.

"The clinical evidence rejects virtually any possiblity of contamination of the grapes in Chile or on the ship or at the port of Philadelphia," a University of California-Davis report commissioned by Chile concluded. "On the contrary, the laboratory results only support the hypothesis that the grapes were accidentally or intentionally contaminated inside the FDA laboratory in Philadelphia."

But the GAO found no fault with the procedures followed by the FDA in testing the grapes for cyanide, saying they were consistent with standard testing procedures.

In addition, the report cited new scientific data refuting the Chilean claims that cyanide would not remain detectable after the journey from Chile. While cyanide does dissipate quickly once injected into fruit, the GAO found, if a spiked grape is refrigerated -- as the grapes in question were during their journey -- then both the dissipation of cyanide and desiccation of the fruit would be dramatically arrested.

Studies by the FDA, the report said, "showed that some poisoned fruit, when refrigerated, retained cyanide at levels comparable to what was found by FDA's Philadelphia laboratory. Some fruit also retained their normal appearance for up to 16 days."

But UC-Davis researcher Lagunas Solar said yesterday, "I find the GAO report deficient, replete with factual errors and omissions and without a scientific basis for the conclusions reached."