A wall of mud and rock swept into the Grijalva river in southern Mexico's Chiapas state, destroying the village of San Juan Grijalva.
At least 16 people are missing, feared dead. The state's governor said a hillside collapsed into the river, creating a wave of mud and water that flattened the community.
Residents of San Juan Grijalva said they were woken on Sunday night by a loud roaring noise as the hillside collapsed.
Many of the village's 600 residents ran for high ground as the landslide swept down the narrow valley.
A week of heavy rains has swollen rivers and left 80% of neighbouring Tabasco state under water.
Mexico's emergency services have been stretched to the limit as some of the worst flooding in more than 50 years has left hundreds of thousands without shelter.