(CNN) -- At least 17 people were killed after a bus carrying more than 50 passengers plummeted into a ravine and plunged into a river in Peru, state media reported.
Rescuers were continuing to search for bodies hours after the crash Thursday, Peru's state-run Andina news agency said.
Dr. William Osorio told the agency that 20 people injured in the crash were at the Hermilio Valdizan de Huanuco Hospital -- with six of them in serious condition.
Police were still investigating the cause of the accident, which occurred on a highway in the central Peruvian region of Huanuco, Andina reported.
CNN affiliate America TV reported that the bus plummeted 200 meters into a river. It was traveling at an excessive speed and also carrying animals onboard, the affiliate said.