254 people died and at least 190 were injured after heavy rains in Mocoa, Columbia, caused a river to overflow, flooding homes, Colombia President Juan Manuel Santos said Saturday.
Santos is on his way to Mocoa, the government said.
The flooding occurred in the early hours of Saturday morning, when most people were asleep.
Many people have been reported missing, and emergency response workers are continuing the search for survivors.
According to firefighters, both electricity and water were no longer available, and the local hospitals were shut down.
Mocoa is a city of 350,000 and the capital of Colombia's Putumayo province. The city sits on the country's border with Ecuador.
Mocoa Mayor Jose Antonio Castro on Saturday told Caracol, "It’s a big area. A big portion of the many houses were just taken by the avalanche but above all the people were warned with enough time and they were able to get out but houses in 17 neighborhoods have basically been erased."