Fifty-three optical employees were hospitalized Wednesday after eating boxed lunches a day earlier.

The Shanghai-based Rinan Optical Co. Ltd. employees suffered from diarrhea and vomiting after eating the meals, which included kidney beans, on Tuesday at noon.

Eight of the 53, who were sent to a local hospital Wednesday morning, showed symptoms of food poisoning, according to the city's food and drug agency.

By Wednesday at noon, 30 of the employees were still hospitalized. The others had returned to work. Three people suffering serious symptoms are being closely observed. Currently their condition has stabilized.

The agency has started investigations into the incident.

Recently, the quality of cooked food, boxed meals and seafood in Shanghai is decreasing. It is mainly due to the broiling weather hovering over the city since July, the food and drug watchdog said.

Some local seafood providers added excessive amounts of preservatives during production and transportation, causing 92 percent of the seafood to pass quality control examinations.

Shanghai has experienced 26 sweltering hot days this summer, nearly three times more than in past years.

On Wednesday Shanghai's temperature hit 35.1 degrees Celsius, the highest to date, although the date marks the beginning of autumn according to the Chinese lunar calendar.

(Xinhua News Agency August 9, 2007)