No exact limit will be imposed on the amount of food each visitor can take into the Expo site, but security staff will stop people with a suitcase or shoulder bag full of edibles, Shanghai's food security authority said on July 2, 2010.

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Security staff will stop people with such large quantities of food at the Expo entrance to avoid both food spoilage in the hot weather and some visitors selling food to others.

The Expo organizer previously planned to set a limit on the amount of food visitors can bring in after some were found with suitcases full of edibles and others were discovered selling their extras to other visitors.

But extra inspections of food would slow down security checks at the entrance, said Xie Minqiang, deputy director of Shanghai Food and Drug Administration.

Nearly a quarter of visitors bring food to the Expo site, doubling the percentage doing so at Expo 2005 Aichi in Japan.

About half Expo Shanghai visitors ate at restaurants and 20 percent bought snacks, including bread and steamed buns, at on-site facilities.

Many visitors bring their own food because prices are perceived to be higher than outside the site. The average cost of a meal is about 40 yuan (US$5.80) per person.

The organizer has suggested visitors bring no more food than needed for themselves, especially in the hot weather. Temperatures soared above 37 degrees Celsius for the second consecutive day yesterday.

No food poisoning incidents have occurred since the Expo opened on May 1 and food security can be ensured at the site, said Xie.

Food and Drug Administration staff have been randomly inspecting about 70 percent of restaurants at the site every day to ensure food safety.

But the number of digestive problems suffered by visitors has been increasing due to the hot weather, said Lin Shengyong, director of the site's commercial administration and service department.

Cooked food, cakes and boxed meals are not allowed into the site because of their propensity to easily turn bad in hot weather, Xie said. Dry food such as breads, biscuits and unpeeled fruit and vegetables, like cucumber, are suggested.

Some visitors who tried to sell food to others have been warned about their behavior. Although they might not be profiting from it, they could still be fined and the food confiscated, Lin said.

The administration has organized a group to inspect raw food imported for foreign pavilion restaurants, Xie said.

The site has more than 200 restaurants, including 150 in public areas and 70 run by the Expo pavilions.