(UPDATED COVERAGE, July 22) As a recall of stone fruit from Wawona Packing Co. expanded to Canada, the California company responded to consumers’ questions, explaining that an Australian importer’s discovery of minute levels of listeria on three peaches spurred the international recall.

The Cutler, Calif.-based company recalled conventional and organic peaches, plums, nectarines and pluots July 19, according to a notice on the Food and Drug Administration website. The fruit was shipped from June 10 through July 12. Canada’s Food Inspection Agency posted its recall notice July 21.

No illnesses have been reported in relation to the recalled fruit.

“Because we do not know the locations of the companies that purchased the products from our direct customers, the company is issuing a nationwide recall,” according to the U.S. recall notice.

Wawona president Brent Smittcamp said July 21 it was still unclear how the listeria monocytogenes contamination may have occurred.

Retailers and wholesalers across Canada and the U.S. received the fruit, which was packed under a variety of brands, including Wawona’s Sweet 2 Eat and Harvest Sweet labels. Wawona spokeswoman Amy Philpott said the company was harvesting and shipping before the recall, but she wasn’t sure for how long.

UPDATED: Wawona stone fruit recall spurred by Australian testsSome retailers, including Costco, Wegman’s and Dierberg’s issued their own recalls. Other retailers known to have received the fruit include Trader Joe’s, BJ’s and Sam’s Club. The fruit is packed in bags, boxes and clamshells, as well as bulk lots. Some of the fruit was exported.

“On July 10 an Australian importer notified Wawona Packing that it had detected within tolerance levels of listeria monocytogenes on three of (Wawona’s) peaches,” according to a statement from Wawona officials that quoted Australian food standards.

Australia, like many other countries, allows for low levels of listeria because levels of less than 100 colony forming units per gram of food “do not present a public risk,” Wawona officials said in the July 21 statement. The peaches that tested positive in Australia had less than 10 units per gram, according to the Wawona statement.

“Because the (FDA) has a zero-tolerance for listeria monocytogenes, upon being notified by Australia, Wawona Packing immediately retained a reputable, private laboratory to test both the Wawona Packing physical plant as well as product,” according to the company’s statement.

“While waiting for the confirmed test results, the compamy stopped production and performed extra cleaning and sanitization measures and conducted more tests. All test results taken after this process have been negative.”

UPDATED: Wawona stone fruit recall spurred by Australian testsThe lab did find listeria on two peaches and one nectarine among the product Wawona had it check. However, when the lab tested other pieces of fruit from the same boxes, all of it was negative for listeria, according to the Wawona statement.

Wawona is maintaining its normal production levels by using outside facilities in the area, Smittcamp said.

The complete list of more than 900 block identification numbers included in the recall is attached to the recall notice.