So far, health officials said, they have taken improperly labeled or unlabeled cheeses from Mexican grocers in Brooklyn and Queens.

It has increasingly shown up in international drug testing, and in some cases is believed to have been included in improperly labeled nutritional supplements.

Scientists have said that the presence of norandrosterone can come from taking anabolic steroids or improperly labeled nutritional substances.

By late last month, investigators had located 2,438 improperly labeled drums at various West German waste-storage sites.

The companies know that they need to fear litigation only if their products are negligently tested, negligently manufactured or improperly labeled.

He was convinced that they were either unsafe or improperly labeled.

One possible explanation is that nandrolone may be contained in improperly labeled nutritional supplements that many athletes use, some scientists have said.

Hunter has said that he believed he ingested the substance from taking improperly labeled and contaminated nutritional supplements.

He said that nutritional supplements, which he called improperly labeled and packaged with quality-control problems, had led to the positive drug tests.

Improperly labeled nutritional supplements may have caused the positive tests, but that does not exonerate the athletes, scientists said.