Officials say all 18 elementary school students buried in a landslide in a mountainous part of southwestern China are dead, while one other person is missing.

The Yiliang county government said on its website that the children were declared dead early Friday about 18 hours after the landslide smothered the school and three farmhouses. It says the missing person was in one of the farmhouses when the landslide struck after 8 a.m. Thursday.

The government says the landslide blocked a river, and its water pooled around the buried buildings, hampering rescue efforts.

Officials have yet to give a cause for the landslide but the area has been lashed by rain and is prone to earthquakes. A series of quakes last month left 81 people dead.