An O'ahu distributor has voluntarily recalled 11,000 pounds of frozen fish after federal investigators found salmonella while testing a parcel of 'ahi.

"Our main concern is safety," Edmund Choy, owner of Choyce Products, said in a news release. "We unknowingly received a tainted package. We immediately issued a voluntary recall and confirmed that our customers do not have 'ahi from that parcel in their inventory."

The frozen fish is most commonly used in poke.

The recall comes after more than 33 cases of the same strain of salmonella — Salmonella paratyphi B — were reported on O'ahu from October to December 2007. State health officials traced the cases to 'ahi that was consumed raw, but they did not link it to a particular eatery or grocery store, or even one distributor.

That means more tainted fish could still be for sale.

U.S. Food and Drug Administration investigators are testing 'ahi samples at the more than 40 distributors on O'ahu to see whether there are other shipments of tainted fish. Meanwhile, health officials point out the recalled fish is not necessarily related to the outbreak since it is unclear what type of salmonella was found in the frozen parcel.

The recalled fish got to O'ahu from Indonesia in early December.

About half of the recalled shipment has been recovered.

The FDA would not comment on the investigation. But a Choyce Products spokeswoman said the company is cooperating with the FDA. She said the company has never had a similar case of tainted fish.

Carroll Cox, president of EnviroWatch Inc., which has been investigating the salmonella reports, commended Choyce Products for voluntarily recalling the tainted fish, but questioned why state Health Department officials and the FDA are not talking about other distributors, wholesalers and stores that possibly sold tainted fish.

"They need to come out and give the public information on this cluster," he said. "Others could have gotten sick and not know why."

He also questioned why it has taken so long for the fish to be tested.

Janice Okubo, Health Department spokeswoman, said state investigators started to look into the salmonella cases in December, though they had been tracking it since the first reports came in.

Tracing the salmonella to a food source was difficult because residents who got sick did not share a common source — they didn't all eat at the same restaurant or shop at the same grocery store.

Federal investigators were called in last month.

Paul Effler, state epidemiologist with the Health Department, said most of those who got sick after eating raw 'ahi experienced relatively mild symptoms, including diarrhea and vomiting. There were no reports of people getting blood-borne infections, which can require hospitalization.

Hawai'i typically has about 300 cases of salmonella poisoning annually. But the cluster of cases tied to raw fish were from a strain that health officials typically see just 10 times a year. The strain has been associated with smoked white fish, unpasteurized milk and alfalfa.

Effler said although the number of cases of the salmonella strain is higher than usual, the contamination is considered low-level because it did not appear to taint a large portion of the original supply of 'ahi.

He pointed out there are more than 220,000 pounds of 'ahi shipped into Hawai'i monthly."It's not like there have been a tremendous number of illnesses given the 'ahi consumed," Effler said.

Reach Mary Vorsino at mvorsino@honoluluadvertiser.com.