WILLISTON - Health officials are still searching for the source of 15 cases of salmonella reported here in late May and early June.

Julie Goplin, an epidemiologist for the State Health Department, said the first case found in Williston was May 23 and the last cases were reported June 14. Health officials said one woman, who was older than 65, died. She has not been identified.

"We reported all cases to the Center for Disease Control and found matches to this strain nationwide. There were 28 others in 17 states … There may be a possible source in all the cases," Goplin said.

A food supplier may be a source of the salmonella, but no link to all the cases has been pinpointed in Williston, she said.

Health officials checked Williston's Economart store, and praised store officials for cooperating in the investigation.

"Of the 15 cases, only five cases had rotisserie chicken. Ten other cases had no link to the grocery store. There is not a common link between the cases," Goplin said.

"The original cases seemed they had a common link to the store, but as we included further cases to the report, we could not determine the same link to the grocery store (Economart)," she said.

Goplin said DNA samples taken in North Dakota and sent to the CDC match samples that were taken in 17 other states.

Mike Kraft, owner of the Williston Economart, said no evidence of salmonella was found in his store by a state health inspection team or by a private company he hired.

Kraft hired Mak-Bea Laboratory of Blue Earth, Minn. to monitor store food handling practices, test for problems and train his staff.

"We have a five-star rating system. Economart was in the excellent range," said Galen Maki, president of Mak-Bea.

"We also did a visual audit of the store. We looked at all the perishable departments. We checked temperatures to see if there were any violations. We didn't find anything that would cause food-borne illnesses," he said. "By watching them working, we could determine they were doing things correct before we came through the doors."

Areas that were tested showed negative results for the salmonella species, Maki said.

"There is no scientific proof that salmonella was present in the store," he said.

"I bought the food and ate it. I had chicken and other products. It was great," Maki said.