(CNN) — A California company has issued a nationwide recall on its romaine lettuce after the lettuce tested positive for salmonella in Wisconsin, according to a statement from the company.

No illnesses have been linked to the lettuce, the statement said.

The Wisconsin Department of Agriculture conducted a random test on romaine lettuce from Tanimura & Antle Fresh Foods, Inc., the company said in a statement, and found the bacteria.

The company has also recalled its romaine lettuce distributed in Puerto Rico and Canada.

The company said it had notified its customers on Tuesday about the recall and told them to “discard any existing product.”

The voluntary recall affects single, whole heads of lettuce with a shelf life of 14 to 16 days after harvest dates from June 25 to July 2, the company said.

“We very much regret the inconvenience that the recall may have caused our consumers and customers,” said company CEO Rick Antle, in the statement. “Food safety and consumer health are our top priorities.”