An explosion took place in a police building in Lishui City, east China's Zhejiang Province, Sunday, but no casualties have been reported. The blast occurred at about 8:03 a.m in a waste explosive warehouse on the sixth floor of the building housing the Public Security Bureau of Qingtian County, local police officers said. Witnesses recalled apart from huge bangs, some window glasses of the building were also shattered amid the explosion. An initial investigation showed the explosion was caused by the self-ignition of the waste explosives confiscated earlier by police. Police are still investigating the cause of the incident. 