Awwal 06, 1432 / April 10, 2011, SPA -- Four people were killed in a cement plant blast Sunday in north China's Inner Mongolia Autonomous Region, local authorities said. A steam boiler of the cement plant in Baolongshan Town of Tongliao City exploded at around 7:40 a.m. Sunday, Xinhua quoted the regional work safety bureau as saying. The cause of the blast is under investigation.