Machines that failed to seal dairy packages were to blame for the food poisoning of about 200 school children in northwest China's Shaanxi Province, a government spokesman said Sunday.

Sickened students?receive medical treatment.

"Some regulating valve shafts of the filling machines were corroded. The fault made the machines unable to completely seal the dairy packages. The packaged milk had gone bad before drinking," said the spokesman after a government work team concluded the investigation.

About 200 middle and primary students in Hanzhong and Ankang cities of Shaanxi started to vomit and had stomach aches after drinking school breakfast milk, supplied by Shaanxi Renrengao Dairy Co. Ltd., a privately-run business, last Monday.

Most of the students have been discharged from hospital, but eight remained for further medical observation, according to the spokesman.

He said compensation packages were being negotiated.