At least 13 people were killed and 61 others injured when a bus went off the road and fell into an 80-meter ravine Monday in Colombia's southwest department of Cauca, authorities said. The bus was overcrowded and most of the victims were indigenous people who traveled to take part in a popular celebration event, according to local media. Among the injured, 15 in serious condition were taken to Popayan, capital of Cauca department, while the rest were sent to other hospitals, authorities said. An investigation was underway to find out the cause of the accident, which happened in good weather conditions. During the weekend, 21 people died in three road accidents across the country. The Colombian Highway Police said the accidents were due to the bad conditions of the vehicles.