Eighteen people were killed and 15 others hurt Wednesday when a bus plunged into a river in the central province of Chanchamayo, Peruvian police said.

First responders are still searching for 21 people who were aboard the bus and remain unaccounted for, Col. Rodorico Cubas told RPP radio.

So far, 18 bodies have been recovered and the injured have been taken to nearby hospitals, he said.

The police chief said that the bus went off the roadway for unknown reasons before entering a tunnel and ended up plunging into the Tarma River, some 370 kilometers (229 miles) from Lima.

Witnesses to the crash told RPP that the bus went down a 50-meter (163-foot) slope into the river and that the weather conditions at the scene had been making it difficult for emergency crews to attend to the injured and recover the bodies. EFE