The blast occurred at the sub-district office in Wulong district’s Chongqing municipality, trapping 27 people.
Thirteen people had been pulled out from the debris, three of whom died during rescue efforts, state-run CGTN-TV quoted the on-site emergency response team as saying.
The accident took place at 12:10 pm local time due to a suspected gas leakage which triggered the explosion and caused the collapse of the canteen building, the municipal publicity department said.
Rescuers are looking for the 14 others buried in the debris, state-run Xinhua News Agency reported.
According to witnesses, people were having lunch in the canteen when the blast took place. A number of people were injured and have been rushed to the hospital; rescue work is underway, Xinhua reported.
China’s ministry of emergency management has dispatched several experts to guide the rescue efforts.
Minister of emergency management Huang Ming has called for efforts to immediately inspect the situation, find out the exact number of victims trapped, determine the cause of the accident and prevent such mishaps from happening again.
More than 150 firefighters and professional rescuers as well as a group of rescue dogs are racing against time to search for the trapped people.
China has in recent months witnessed explosions in restaurants, killing and injuring many people which are largely blamed on gas leaks.