SYDNEY • Australian health officials issued a national recall of packaged lettuce and other salad products after 28 cases of salmonella poisoning in the state of Victoria.

The outbreak on Thursday, at the height of Australia's summer, the salad-eating season, has been traced to more than 20 products of bagged lettuce and other salad leaves produced by Tripod Farmers.

They are sold mostly through major supermarket chains.

Two people have been admitted to hospital, and more cases are expected in the coming days, said Dr Finn Romanes, the senior medical adviser at Victoria's department of health. Salmonella usually strikes between six and 72 hours after the bacteria are ingested.

"This particular strain of salmonella that we have detected, Salmonella anatum, usually only occurs in very small numbers in Victoria," Dr Romanes said at a news conference in Melbourne on Thursday. "So far this year, we have been notified of 28 cases."

He said the common factor was packaged salad, and some products from the company had tested positive for the strain of salmonella. The cause of the contamination had not been determined, he said.

A salmonella infection causes gastroenteritis that can last many days. It is not usually fatal, but the health department has warned that elderly people, young children or those whose immune systems are compromised may be at more serious risk.

Mr Frank Ruffo, managing director of Tripod Farmers, said the company had issued a voluntary recall of some of its products, and was working closely with the authorities.

Dr Romanes said the anatum strain of salmonella was uncommon and could be traced back to chickens and eggs, and possibly chicken-based fertiliser.

He said processed salad products were usually washed three times before being packaged and distributed to supermarket chains.

NEW YORK TIMES