A gas explosion tore through a coal mine in northern China overnight on Friday, killing 42 people and trapping 66 others half a kilometer underground, central government authorities said. A total of 528 people were working in the Xinxing mine in Heilongjiang province at the time of the 2:30 a.m. explosion, the State Administration of Work Safety said in a statement. It added that 389 managed to escape after the blast. China Central Television reported that 42 were dead, 31 were rescued and the others were trapped about 500 meters underground. The report said the explosion was caused by a gas buildup. It shattered windows within 20 meters of the mine shaft. A man answering the phone at the mine said an unknown number of people were injured. He did not want to give his name, as is common among Chinese officials. The mine is located near the border with Russia, about 400 kilometers northeast of the provincial capital, Harbin. It is run by one of China's top 520 state-owned enterprises, according to the Web site of its owner, the Hegang branch of the Heilongjiang Longmei Holding Mining Group. The site says the Hegang branch has more than 88,000 employees. China's mines are the world's deadliest, with unregulated operations accounting for almost 80 percent of the country's 16,000 mines. The closing of many small, dangerous mines halved the average number of miners killed to about six a day in the first half of this year, the government has said. Most accidents are blamed on failures to follow safety rules, including a lack of required ventilation or fire control equipment. A similar blast at the Tunlan coal mine in northern China's Shanxi province killed 77 people in February, China's worst industrial accident in a year.