At least six people were killed and more than 30 others injured when a bus plunged into a ravine on the so-called "highway of death" in Bolivia's Los Yungas region, police said.

The accident happened Tuesday morning near Hierbani, a town about 60 kilometers (37 miles) from La Paz, when the bus went off the road and into a 250-meter (820-foot) ravine, highway patrol chief Col. Gabriel Abella said.

The bus was carrying coca growers from La Asunta, a town in Los Yungas, to a meeting in La Paz.

The bodies of the dead - four men and two women - were taken to the hospital in Chulumani, a town between La Paz and La Asunta, while the injured were transported to hospitals in La Paz.

The "highway of death" winds through several towns in Los Yungas, descending from highlands valleys at about 4,000 meters (13,114 feet) above sea level into the Amazon region.

The government has been trying for years to reduce the number of traffic accidents in Bolivia.

President Evo Morales's administration enacted a law in January 2010 that cracked down on bus drivers caught working drunk, inexperienced drivers and drivers who work excessive hours.

The law's goal is to reduce accidents, which kill an average of 1,000 people and injure about 40,000 others annually in this Andean nation, according to International Automobile Federation figures. EFE