MEDAN, Indonesia (AP) — Torrential rain triggered flash floods and a landslide on Indonesia’s Sumatra island, leaving at least 12 people missing, officials said Saturday.

Tons of mud, rocks and trees rolled down from a mountain late Friday, reaching a river that burst its banks and tore through mountainside villages, said Budiono, who heads the local search and rescue agency.

Worst hit was Simangulampe, a village near the popular Lake Toba in North Sumatra province, where several people buried under tons of mud and houses were damaged, said Budiono, who goes by a single name like many Indonesians.

He said relief efforts were hampered by blocked roads covered with thick mud, debris and giant rocks, and rescuers were still searching for the 12 missing people Saturday.

National Disaster Management Agency spokesperson Abdul Muhari said a villager was rushed to a nearby hospital with serious injuries after the landslide hit his house. He said at least 12 houses, a church, a school and a hotel were damaged by the disaster, forcing about 50 families in the village to flee to a temporary government shelter.

Photos released by the agency showed damaged homes, along with a church, a school and a hotel covered by tons of rocks.

Authorities were still collecting information about damage and possible casualties, Muhari said.

Seasonal rain from about October to March frequently causes flooding and landslides in Indonesia, an archipelago of 17,000 islands where millions of people live in mountainous areas or near fertile flood-plains.

The 1,145-square-kilometer (440-square-mile) Lake Toba, formed out of an ancient supervolcano, is a popular sightseeing destination on the island of Sumatra and one of 10 stunning natural attractions in Indonesia that the government aims to develop as magnets for international tourists.