A Kona ocean fish farm this week will resume harvesting after laboratory tests concluded there were no detectable levels of a pet food contaminant in the flesh of its fish, a variety of kahala sold as Kona Kampachi.

Kona Blue Water Farms halted harvesting in one of its six open-ocean cages after learning that some of the fish food that it bought from the Skretting firm in Vancouver contained traces of the contaminant melamine. The flesh of 10 fish from the cage being harvested was sent to a private laboratory, which concluded there was no melamine detectable in the fish, said Mike Wink, Kona Blue chief executive officer.

He said samples from each of the other cages also would be tested before those cages are harvested, but he does not anticipate problems.

"While we were confident our fish would test clean due to the minimal amount of tainted feed that was used, we took the precautionary step to shut down sales until we had proof that our Kona Kampachi continues to meet our highest standards of product purity and quality," Wink said.

The fish farm's woes are part of a nationwide inquiry into pet food with contaminants that have been traced to ingredients from China.

An unknown number of dogs and cats in the U.S. became ill or died from eating tainted pet food, but authorities said that the levels of contaminant in farm animal feed were much lower.

The U.S. Department of Agriculture said yesterday that an estimated 56,000 pigs that ate some of the affected food were safe to be eaten. The hogs had been in quarantine in seven states, not including Hawai'i.

Another 80,000 poultry are still being held until a test can be developed that can detect melamine in bird flesh.

The U.S. Department of Agriculture and the Food and Drug Administration said that even if humans eat meat or fish contaminated with melamine, levels are so low that there is minimal risk.

Melamine is a chemical with a range of uses, among them medical. It is employed in the manufacture of foam, countertops, flame retardants, fertilizers and floor tiles.

Both the state departments of Agriculture and Health said yesterday that they aware of the problem and tracking it, but are leaving the actual pet and fish food contamination investigation to the FDA.

"We haven't done any testing here. We have been doing spot checks on the dog and cat food counters, and larger retailers seem to be making an effort to alert consumers and remove the product from their shelves," said Janice Okubo, public information officer for the Department of Health. As an example, she said, Longs stores have posted information sheets about the recall of certain products, and Costco has mailed customers suggesting they return potentially contaminated pet foods.

The state Department of Agriculture laboratory is able to conduct tests for melamine, but thus far all testing has been done by the FDA, said Janelle Saneishi, the department's public information officer.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.