At least 14 people were killed after being swept away by flash floods in Indonesia's North Sulawesi, an official said on Tuesday, as the search for the missing continued.

Heavy rain early on Monday triggered flash floods on the island of Siau, located in the region of Siau Tagulandang Biaro, said Nuriadin Gumeleng, a spokesperson for the local rescue agency.

Sixteen rescuers have been deployed to search for four people who remain missing on Tuesday, Gumeleng told Reuters, adding that 18 people had been injured so far.

"We continue to collect data from local residents in case there are more missing people," he said.

As of Tuesday, main roads in the affected areas were still covered by rocks, debris and thick mud, Gumeleneg said.

At least 444 people have been evacuated to local schools and churches after the flash floods, the country disaster mitigation agency spokesperson Abdul Muhari said in a statement.

Authorities have deployed excavators to clear roads that have been blocked by the debris and mud, he said.

The floods also destroyed hundreds of houses and government buildings, North Sulawesi governor Yulius Selvanus said.

The flash floods took place in the peak of the wet season in Sulawesi island, as forecast by Indonesia's weather agency.

The islands of Java, Sulawesi, Maluku, and Papua are expected to experience their peak wet seasons over January and February this year, bringing more risks of floods, the weather agency had said.

Rain in other parts of Indonesia like Sumatra and Borneo reached its peak in November and December last year.

Last November, cyclone-induced floods and landslides killed more than 1,000 people in Sumatra, with hundreds still missing. Green groups say deforestation linked to mining and logging exacerbated the impact of the floods.