Three children have died and another thirty-five people sickened?after drinking milk from two local dairies?in northwest China's Gansu Province, the local government said Friday.

An initial investigation showed that the victims were poisoned by nitrite, Xinhua News Agency reported.

The?victims, mostly children under 14, now are being treated at two leading hospitals in Pingliang City, according to the press released by the city government and health bureau.

It said one of the patients was in critical condition and the other cases were stable.

The two dairies were sealed off after the accident and their managers were being probed.

At present the case is under further investigation.

China's quality inspection agency on April 3 ordered 426 dairy firms to halt production as part of a campaign to clean up the industry.