People in a small city in southern Colombia searched desperately Sunday for loved ones after heavy rains sent floodwaters, mud and debris surging through homes, killing at least 207 and leaving many injured or missing.

The streets of Mocoa were covered in thick sand, mud and tree limbs from the rivers and forest that surround the city. There was little drinking water and no power, which forced authorities to suspend the search-and-rescue effort during the night.

President Juan Manuel Santos, who has declared Mocoa a disaster area, said that at least 207 were killed but that the death toll was changing “every moment.” Authorities said 200 others, many of them children, were injured and that just as many were unaccounted for amid the destruction.

People dug through the ruins, salvaging what they could of their possessions and looking for the missing. Dozens were at a hospital looking for family members who were not on the list of those confirmed injured or dead. Others frantically knocked on the doors of neighbors, hoping to find someone with information about their relatives. Search-and-rescue teams also combed the rubble for signs of life.

The devastation was caused by intense rains that led the rivers that surround Mocoa, a city of about 40,000 nestled amid forested mountains, to overrun their banks. Muddy water and debris quickly surged through the city’s streets, toppling homes, ripping trees from their roots, lifting cars and trucks and carrying them downstream. The floods struck before dawn, and many didn’t have enough time to climb on top of their roofs or seek refuge on higher ground.

Santos blamed climate change for the avalanche, saying the accumulated rainfall in one night was almost half the amount Mocoa normally receives in the entire month of March. With the rainy season in much of Colombia just beginning, he said, local and national authorities need to redouble efforts to prevent a similar tragedy.

The crisis will probably be remembered as one of the worst natural disasters in Colombia’s recent history, though the Andean nation has experienced even more destructive environmental catastrophes. Nearly 25,000 people were killed in 1985 after the Nevado del Ruiz volcano erupted and triggered a deluge of mud and debris that buried the town of Armero.