BUKITTINGGI, Indonesia (Reuters) -The number of people killed by flash floods and mud slides in Indonesia's West Sumatra province has risen to 52, and more than 3,000 people have been evacuated, authorities said on Tuesday, with heavy rains expected until next week.

Torrential rain on Saturday evening triggered flash floods, landslides, and cold lava flow - a mud-like mixture of volcanic ash, rock debris and water - in three districts in West Sumatra province. On Monday, the death toll was 43.

The cold lava flow, known in Indonesia as a lahar, came from Mount Marapi, one of Sumatra's most active volcanoes. More than 20 people were killed when Marapi erupted in December. A series of eruptions have followed since.

Of the 52 dead, more than 45 have been identified, West Sumatra disaster agency spokesman Ilham Wahab said. Local rescuers, police and military will continue searching for 17 people who are still missing, he added.

Ilham said 249 houses, 225 hectares (556 acres) of land, including rice fields, and most of main roads in the three districts were damaged. The floods have receded since Sunday.

"Besides searching for the missing persons, we will focus to clean the main roads from the mud, logs, large rocks brought by the floods onto roads and settlements," Ilham said.

As of Tuesday, 3,396 people have been evacuated to nearby buildings, the head of national disaster and management agency BNPB, Suharyanto, said in a statement.

BNPB has distributed tents, blankets, food, hygiene kits, portable toilets, and water purifiers, said Suharyanto, who uses a single name, like many Indonesians.

However, the distribution has been impeded as most roads were covered by mud and debris, he said.

Heavy rains in West Sumatra province are still expected until next week, said Dwikorita Karnawati, the head of Indonesia's meteorology agency, BMKG.

"This means that we need to be alert about the potential flash floods and landslides at least until May 17-22," she said.

BMKG also warned people to stay away from hillsides that are prone to landslides.

Roza Yolanda, 23, was relaxing at her house when the heavy rain fell over the weekend. Water poured into her house seconds after a power outage.

"I was dragged out of my house by the floods into the streets, around 200 metres," Roza said. "My neck was struck down by logs, I hit walls, windows."

She was floating for about 15 minutes before being saved. Roza, who suffered bruising over her entire body, said her mother is safe but her father was still missing.

(Reporting by Ananda Teresia; Editing by Christian Schmollinger and Gerry Doyle)

By Aidil Ichlas