Food and Drug Administration chief Frank Young said federal investigators have traced the source of cyanide-laced grapes to a Chilean producer who shipped the tainted fruit to the United States, but no arrests were imminent.

"We don't have the exact person who would have done it but we do have a lot of information and we can trace back, with a paper trail, to the small producer where this particular crop came from," Young said Sunday on NBC's "Meet the Press" news show.Young confirmed that authorities know the name of the firm that produces the fruit, but he refused to divulge it. But he said authorities believe the tampering was done in Chile.

The FDA imposed a four-day ban on Chilean fruit that ended March 18 after authorities discovered a non-lethal dose of cyanide had been injected in two grapes contained in a shipment from Chile.

The deadly chemical was found during a stepped-up inspection program after the U.S. Embassy received two anonymous calls warning of the poisoning of Chilean fruit.