(May 7) Canadian health officials are concerned about a second occurrence of high levels of a chemical found in red potatoes that causes illness in humans, but the store where the potatoes were most recently found may have isolated them in time to avoid further problems.

The Canadian Food Inspection Agency, Ottawa, with the help of the Canadian Produce Marketing Association, Ottawa, is warning the public to avoid consumption of red potatoes purchased between April 16 and April 26 at the Killarney Market retail store in Vancouver, British Columbia.

The store has voluntarily recalled the affected product, but Tito Chiang, co-owner of the store, said he had heard no other complaints about the potatoes from the company's 8,000 customers. He added that he was expecting a report from CFIA within the next couple weeks.

Chiang said representatives from two retail chains in Canada had called the store to inquire about the situation and told him they had not been contacted by the CFIA.

Marie-Claude Thibault, director of health and food safety for CPMA, said officials were alerted to an excessive amount of gycoalkaloids in the potatoes when a customer of the market complained of a sore mouth after eating some of the potatoes.

Glycoalkaloids are naturally found in the outer surface and peels of potatoes. Inspectors found the potatoes at the customer's home had 42 milligrams of the chemical per 100 grams of potato. Acceptable levels are 20 milligrams per 100 grams, Thibault said.

In addition to a sensation of burning in the mouth, excess glycoalkaloids can cause vomiting, diarrhea or gastrointestinal infection. In extreme cases, death can occur.

When the inspectors went back to the store to test more potatoes, a new shipment had arrived and was placed with the contaminated potatoes. Still, the potatoes tested at the store were over the acceptable levels despite being diluted by clean potatoes, Thibault said.

Thibault said officials still did not know why or how the potatoes contained such high levels of the chemical, adding that a similar problem occurred in March. She said the new potato crops were tested under a variety of conditions, but surmised that particularly cold weather in Canada this year, which might have fallen outside the range of tested conditions, might have been to blame.

She said it could be a while before scientists determine the cause for the contamination, due to the number of factors that could have affected the potatoes.

"To replicate all those conditions in a lab is not easy," Thibault said.

Thibault said CPMA was working to inform retailers of the potential for similar outbreaks. In this case, the retailer was an independent grower. But in subsequent cases, if major chains were involved, the problem could be much more widespread, she said.