Three people remained hospitalized on Thursday in Shenzhen following a mass food poisoning that befell more than 300 factory workers on Wednesday in Shenzhen, the southern Chinese boom city.

A manager of the Hong Kong-invested company that produced hardware and plastic in the outer Longgang District in the Guangdong Province city, said the workers suffered headaches, nausea and vomiting after eating Chinese cabbage and kidney beans for lunch in the staff canteen. They were sent to five local hospitals for treatment.

A health department spokesman said most of the patients were allowed to go home after treatment, but 36 of the cases were serious. Five people had to spend the night in hospital.

He said three patients were still under treatment and observation on Thursday.

Investigators suspected undercooked kidney beans as the cause of the illness.

Experts said kidney beans contained lectin, a toxic agent that could cause diarrhea if the beans weren't heated thoroughly.

Undercooked kidney beans had hospitalized 248 teenage students in the southwest Yunnan Province last month.

(Xinhua News Agency January 10, 2008)