The two fish farms that used the feed had kept their fish off the market until the tests could be completed.

Dr. David Acheson, assistant commissioner for food protection, said fish being raised at Kona Blue in Hawai'i and American Gold Seafoods in Washington state were found negative for the chemical melamine.

Mike Wink, chief executive officer of Kona Blue, told The Advertiser earlier this week that tests had shown the fish had no detectable levels of the contaminant.

The questionable feed was also sold to 196 fish hatcheries in the United States. Because those fish are small and the feed has been recalled, Acheson said the FDA believes there no longer is any public health concern from them.

The FDA on Tuesday cleared for use 56,000 pigs given feed that included scraps of pet food contaminated with melamine.

Melamine contamination has been blamed for the deaths of an unknown number of dogs and cats, resulting in the recall of dozens of pet food brands.

Since the problem was discovered, 46 shipments of protein concentrate from China have been detained and are being held until the companies that produced them can prove the material is free of melamine, Acheson said.

"Any vegetable protein concentrate from China is not going to be imported until we are sure that it is negative," Acheson said.