Hours of heavy rain caused large volcanic rocks to roll down one of Indonesia's most active volcanos into two of the worst-hit districts on Sumatra island
Hours of heavy rain caused large volcanic rocks to roll down one of Indonesia's most active volcanos into two of the worst-hit districts on Sumatra island AFP

Rescuers recovered more bodies on Tuesday after flash floods and cold lava flow on Indonesia's Sumatra island over the weekend killed at least 50 people and left another 27 missing, the country's disaster agency said.

Hours of heavy rain caused large volcanic rocks to roll down one of Indonesia's most active volcanos into two of the worst-hit districts on Sumatra island Saturday evening while flooding inundated roads, homes and mosques.

"Based on reports, Suharyanto (BNPB chief) said victims who died due to the disaster was recorded to 50 people," agency spokesman Abdul Muhari said in a statement, raising the death toll by six.

He said 27 people were still missing and 37 had been injured, while 3,396 people had been evacuated from the affected areas.

Suharyanto, who goes by one name, said in the statement that the death toll could rise further and called for heavy equipment to be deployed to help the search effort.

"The data will continue to develop. To help find (victims) who are still missing, the heavy equipment must come in as quickly as possible," he said.

He added that the search was urgent as rescuers only had a "golden time" of six days to find survivors.

Aid deliveries were being carried out using air and land routes, some of which required emergency bridges, after the flooding and cold lava flow cut off some road access in the worst-hit areas, Suharyanto said.

Muhari on Monday said 71 houses were completely swept away and 125 houses were moderately damaged by the flooding and cold lava flow.

Cold lava, also known as lahar, is volcanic material such as ash, sand and pebbles carried down a volcano's slopes by rain.

Flooding has affected a total of four districts in West Sumatra -- Agam, Tanah Datar, Padang Panjang and Padang Pariaman -- according to authorities.

Residents described the thundering noise when large volcanic rocks bowled down from Marapi and their fear as terrifying rains inundated their neighbourhoods.

Indonesia is prone to landslides and floods during the rainy season.

In 2022, about 24,000 people were evacuated and two children were killed in floods on Sumatra island, with environmental campaigners blaming deforestation caused by logging for worsening the disaster.

Marapi is one of Indonesia's most active volcanos.

In December, it erupted and spewed an ash tower 3,000 metres (9,800 feet) into the sky, taller than the volcano itself.

At least 24 climbers, most of them university students, died in the eruption.