HARBIN -- One person died and 203 people were poisoned after eating breakfast at a hospital restaurant in northeast China's Heilongjiang Province on Monday, hospital sources and the local government confirmed.

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A lethal rat poison, fluoroacetamide, was confirmed on Tuesday to be the cause of the food poisoning, according to investigations by local police and the Heilongjiang Provincial Disease Control Center. No further details were given by the provincial authorities.

All the victims ate porridge, and investigators suspected the water was contaminated with rat poison.

By noon on Tuesday, more than 3,000 acetamide inoculations, a specific antidote for fluoroacetamide, had arrived at the provincial capital Harbin to treat the victims, local health authorities said.

This included 290 doses provided by neighboring Jilin Province and 3,000 by the state drugs reserve authorities at the request of the Ministry of Health.

Heilongjiang had only about 30 doses of acetamide, health authorities said.

The victims included patients and staff at the Heilongjiang Provincial Hospital of Traditional Chinese Medicine. Most complained of nausea and diarrhea shortly after eating breakfast at the hospital's restaurant.

The most serious case, 77-year-old Du Qingrong, died on Monday afternoon. She was hospitalized on Friday for cardiovascular disease.

Hospital sources said all the other victims were out of danger by Monday.

The restaurant was shut down immediately and the local health watchdog took samples of the food for analysis on Monday.

The hospital is among the largest and best-equipped medical institutions in the provincial capital of Harbin.