Chinese officials say all 18 elementary school students buried in a landslide in southwestern China on Thursday are dead, while one person is missing.

Yilian county officials said the students were confirmed dead early Friday, about 18 hours after the landslide buried a school and three farmhouses in the village of Zhenhe. Officials said one person is missing and one was injured and is receiving treatment at a temporary medical station.

The government said the landslide blocked a river, and water pooled around the buried buildings, hampering rescue efforts and forcing the evacuation of around 800 people.

Officials said about 2,000 residents, police, medics and military personnel rushed to the scene to begin rescue efforts.

Normally, the students would not have been in school, because China is in the middle of a week-long national holiday period. But officials say the students were making up for classes that were canceled following last month's earthquake which left 81 people dead.

Southwestern Yunnan province is a mountainous, earthquake-prone region. Last month's 5.6-magnitude temblor devastated several villages and displaced more than 200,000 people.