An explosion ripped through a karaoke bar in northeastern China, killing 25 people, including high-school students celebrating the end of their gruelling university entrance exams.

The popular bar in Tianshifu, a coal-mining town in the rustbelt province of Liaoning, was destroyed by the force of the blast late on Wednesday. Rescuers searched for survivors and tried to recover bodies from rubble, all that remained of a two-storey building. At least 33 people were taken to hospital, four of them in serious condition, and most had sustained broken bones.

It was China’s deadliest fire since 26 people died when flames tore through an illegal bar in the southern city of Zhongshan in 2005. That bar had lacked fire extinguishers and its emergency exit was too narrow.

Police were unable to give a reason for the disaster at the Tianying Karaoke Hall and Bath House. However, China has a dismal fire safety record. On Christmas Day 2000, more than 300 people were killed when fire engulfed a nightclub in Luoyang city in the central Henan province. Many of the victims of this latest tragedy were students letting off steam after completing university entrance exams, when young people find themselves under greater pressure than at any time in their education as they compete for a tiny number of places.

One local girl said: “Some of the victims were teenagers around 18 to 19.” Also among the dead was the owner of the venue. His wife and other staff were being questioned by police.

A man who visited the scene described hearing a large explosion. “There was a very loud noise and all the windows near the site were shattered,” he said. The blast also brought down nearby power lines, pitching the town of 40,000 into darkness.

Children were the chief victims of two of the worst fires since the 1949 Communist takeover. A total of 288 children were among the 323 people killed when a blaze tore through a cinema in the north west in December 1994. Many of the children died because they were told to remain seated while government officials were evacuated. That disaster was eclipsed only by a 1977 cinema inferno, also in the northwestern region, in which 694 people died, 597 of them children.

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