The blast, which a preliminary probe indicated might have been caused by a gas leak, occurred early Monday on the sixth floor of the building in the coastal city of Weihai in eastern Shandong province, resulting in a fire, Xinhua News Agency reported.
The fire was extinguished in 20 minutes, but all the seven floors of the building sustained damage, rescuers and witnesses said. It was not immediately known how many people lived in the building.
A search was underway for the four people missing while rescue work was continuing, the news agency said. A report on the condition of those injured was not available.
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