Three children have died in north-west China from suspected poisoning after drinking milk from two local dairies, state media says.
Thirty-five others, mostly children, are being treated at hospitals in Gansu province, officials said.
An initial investigation showed that the victims were poisoned by nitrite, a chemical used in the curing of meat.
The two farms have been sealed off and an investigation is under way, Xinhua news agency reported.
A joint statement by the Pingliang city government and health bureau said one of those being treated was "in critical condition and the other cases were stable".
This is the latest in a series of food safety scandals to hit the dairy industry.
Last week, China's quality inspection agency shut down nearly half of the country's 1,176 dairies as part of a campaign to clean up the industry.
In 2008, at least six babies died and another 300,000 were made ill by drinking infant formula tainted with melamine.
The industrial chemical was added to dairy products to make them seem high in protein.
The scandal led to a worldwide recall of Chinese dairy products and was a major embarrassment for the country's Communist leadership.
Beijing later vowed to constantly monitor milk quality to restore consumer confidence.