At least 12 people were killed and 30 others injured when a bus plunged into a ravine early Thursday in the eastern Bolivian province of Santa Cruz, the La Paz daily El Deber reported on Thursday. The accident occurred near Comarapa, a city located about 241 kilometers (149 miles) from Santa Cruz city. The Transporte Tupiza lines bus was traveling from the Andean province of Potosi to Santa Cruz when it went off the highway and plunged into a 100-meter (327-foot) ravine. The cause of the accident is under investigation, Santa Cruz province police chief Sabino Guzman said. Police and firefighters are working at the accident scene and the death toll could rise since more bodies may be in the wreckage. The injured were taken to San Martin de Porres Hospital in Comarapa, El Deber said. Highway accidents kill an average of 1,000 people and injure some 40,000 others each year in Bolivia, government figures show. 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.