At least 34 people have died and 16 more were missing after flash floods and cold lava flow from a volcano hit western Indonesia, a local disaster official said Sunday.

The disaster hit two districts in West Sumatra province on Saturday evening after hours of heavy rain caused flooding and sent sweeping ash and large rocks down Mount Marapi, the most active volcano on the archipelago's Sumatra island.

He said the search effort involved local rescuers, police, soldiers and volunteers. Agam and Tanah Datar districts were hit at around 10:30 pm (1530 GMT) on Saturday, according to Basarnas search and rescue agency.

Earlier, Basarnas said 12 people had died including several children after the flash floods and cold lava flow.

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

Nine bodies were identified earlier on Sunday, including those of a three-year-old and eight-year-old, head of the local rescue agency Abdul Malik said in a statement. "Today, we will continue the search in the two districts," he said.

Authorities dispatched a team of rescuers and rubber boats to look for the missing victims and to transport people to shelters.

The local government set up evacuation centres and emergency posts in several areas of the two districts.

Bd pratidin English/Lutful Hoque