Officials do not forbid visitors from bringing food into the Expo park but suggest they not do it on concerns of food safety, said a report in the Oriental Morning Post on Friday.

As the mercury continues to climb, food will go bad easily, especially after being in bags for hours, said an anonymous official with the Business Service Department of the Bureau of Shanghai World Expo Coordination.

"We have seen rising cases of diarrhea recently, some resulting from consuming bad food brought in by visitors," he said.

"If you do want to bring in food, choose those with a long shelf life," he said, warning that a visitor's Expo tour can be ruined by eating stale food.

He pointed out that there is no need to bring in food such as bread and porridge because visitors can buy them at the Expo park at almost the same price as outside the park, and the quality of food sold at the park is guaranteed.

Selling food at the Expo park without certificate is strictly banned, the official said, responding to reports that some visitors have brought in "a good store of food" to the park for sale.

A regulation restricting the quota of food that a visitor can take into the park is in the works, he said.