At least 20 road construction workers have been killed in a blast while working inside a tunnel in central China, officials said.

The explosion on Saturday in Hunan province also injured one person, according to provincial work safety officials.

The blast occurred when a vehicle was unloading explosives in the tunnel on a road under construction between Yanling and Rucheng in Hunan, the official Xinhua news agency said.

Twenty workers died in the blast and one body has been recovered, Xinhua said.

Four other workers escaped with injuries, and one was taken to hospital in a critical condition.

Accidents and explosions are common in China due to lax enforcement of safety standards.

In November, an explosion in southwestern China killed at least seven people and injured about 200.

It was caused by three explosives-laden vehicles that caught fire and destroyed a garage and a food warehouse.

Source: Agencies