The U.S. Food and Drug Administration yesterday said its own tests confirmed those of fish farm Kona Blue, which found no detectable levels of the chemical melamine in fish in the firm's open-ocean cages off Kona.

The fish were tested after the FDA learned they had been given feed contaminated with melamine, an industrial chemical traced to fish food constituents imported from China. Similar animal-food contamination has been reported around the country, and has killed some dogs and cats.

The FDA tests, conducted on fish samples provided by Kona Blue, found no presence of melamine, said Doug Arbesfeld, senior communications advisor for the FDA. Kona Blue CEO Mike Wink announced Tuesday that the firm's own tests, conducted by an independent laboratory, showed no detectable levels of the chemical.

Arbesfeld added that five federal agencies conducted a risk assessment and concluded there was minimal risk to humans, even if they ate flesh containing detectable levels of melamine.

Meanwhile, the FDA was accused of being slow to respond to evidence that tainted feed had been used at the fish farm.

"They had the information for more than a week before they responded," said Carroll Cox, president of Envirowatch, a non-governmental environmental monitoring organization.

He said the FDA was informed at least two weeks ago by Vancouver firm Skretting that it had shipped contaminated fish food to Kona Blue.

Cox said he has asked FDA to investigate the delays.

"This was in the open ocean. They should have been more quick in responding," Cox said.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.