image copyrightBarcroft Media/Getty Imagesimage captionRescuers are trying to pump water out of the tunnel

A rescue mission is under way to save 14 workers trapped in a flooded tunnel being built in southern China.

Teams are pumping water out of the highway tunnel to find the workers who were caught when it collapsed in the early hours of Thursday.

Hundreds of rescuers, along with 22 fire trucks and five pumping stations, are trying to locate the workers.

Investigators are trying to discover what caused the flooding at the tunnel in Zhuhai, Guangdong province.

Construction workers heard strange noises about 1km (0.6 miles) inside the tunnel, officials say.

An evacuation was ordered at around at 03:30 local time (19:30 GMT on Wednesday), but water began gushing into the tunnel and 14 of the workers could not make it out.

"We feel deeply guilty and deeply blame ourselves," said Yan Dawu, deputy general manager of the construction company.

The area where they were working is under a reservoir, according to reports.

The local fire department has dispatched 19 vehicles and 100 people to take part in the rescue effort, and crews have arrived from other areas, China's Global Times reported.

A rescue headquarters has been set up at the site, local media say.

In March, two workers were killed in the same tunnel when a wall caved in and they were struck by falling stones.

The Xingye Highway Express Line is a highway that runs north to south through Zhuhai city, according to local media.