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BOGOTA (Reuters) - A landslide killed at least four people and left 18 missing in southwest Colombia, authorities said on Wednesday, as the country grappled once again with the deadly pairing of heavy rains and poor infrastructure.

Landslides are common in rural, mountainous areas of Colombia, especially during wetter parts of the year. In April more than 300 people died in a landslide in Mocoa, Putumayo.

Warnings of flash flooding on Tuesday night near the town of Corinto, which sits at the foot of one of the country’s Andean ranges in Cauca province, came too late, some residents told local media.

Videos on social media showed water rushing down darkened streets as rain-swollen rivers overflowed and sent mud and rocks down onto buildings.

President Juan Manuel Santos visited Corinto on Wednesday to promise aid to its 30,000 residents, as rescue workers continued to search for the missing.

The government said more than 3,000 people were evacuated from a nearby area before the landslide struck Tuesday evening.

The government will pay rent for those left homeless and help with funeral expenses, Santos said. The local school, which partially collapsed, may have to be relocated, he said.