(Adds details) By Chris Buckley BEIJING, July 5 (Reuters) - An explosion ripped through a nightclub in northeast China as patrons celebrated a birthday party, killing 25 people and injuring dozens inside and outside the building, state media reported on Thursday. It was not clear what caused the blast which occurred at about 9 p.m. on Wednesday in Benxi county, Liaoning province. "At the time of the explosion, quite a few people were attending a birthday party at the karaoke bar and there were some pedestrians on the main road in front of the club, so the casualties were serious," the official Xinhua news agency said. Windows were smashed and some houses had damaged roofs near the club, while a high-voltage power line was cut off by the blast, leading to a blackout in the Tianshifu township until Thursday morning, the state news agency said. After authorities finished rescue efforts on Thursday, Xinhua cited provincial officials as saying 33 people were also hurt. The owner of the club, comprised of a public bath, a karaoke bar and a restaurant, was killed in the blast and police have held his wife and staff at the club for questioning, Xinhua said. A county official at the scene told Reuters that investigators were trying to work out whether the blast was accidental or deliberate. "It's too early to announce any conclusions," said the official, who gave his surname as Chi. The Communist Party chief of Liaoning province, Li Keqiang, ordered harsh punishment of anyone found to be responsible for the explosion, the China News Service said. Also on Wednesday night, a fire swept through a cinema complex in Hengyang city in central Hunan province. Xinhua reported that one person died. (Additional reporting by Beijing Newsroom and Guo Shipeng)
