At least 43 people have now been confirmed killed in flash floods that devastated Indonesia's West Sumatra province, officials said Monday.

Rescuers were looking for 15 more people who remain missing from the disaster triggered by torrential rains.

The cold lava flood, triggered by heavy rains high on Mount Marapi, swept through several districts of West Sumatra province late Saturday, said Abdul Muhari, spokesperson for the National Disaster Management Agency.

Rescuers found more bodies as they expanded the search area, Muhari said, and the death toll was likely to increase.

The 2,891-meter Mount Marapi is one of Indonesia's most active volcanoes, with a history of eruptions and volcanic mudflows, known as lahars. The mountain had shown increased activity for weeks before the weekend deluge.

Lahar floods are particularly dangerous because they can occur with little warning and move rapidly, carrying a mix of mud, rock, and debris.

Indonesia is prone to earthquakes and volcanic activity due to its location on the Pacific "Ring of Fire," an arc of seismic faults around the Pacific Ocean.

The country also experiences frequent flooding during the rainy season, which typically runs from November to April.

The government has deployed search and rescue teams, along with the military and police, to help with the relief effort, Muhari said.

Emergency shelters have been set up for displaced residents, and officials are distributing food and water to affected communities, he said.

The flood is the latest in a string of disasters to hit Indonesia this year, including earthquakes and landslides.

The country has been grappling with the challenges of climate change, which scientists say is making extreme weather events more frequent and intense.