Rescuers were pumping out water Thursday to try to find 14 construction workers trapped by a flood in a highway tunnel being built in southern China.

The rescuers have not been able to contact the workers missing since the 3:30 a.m. flood, the Zhuhai city emergency management department said in an online post.

“Rescue work is proceeding in an intense and orderly way,” it said.

Workers were about 1.1 kilometers (0.7 miles) from the entrance to the tunnel when a strange noise was heard and material started falling from the top of the tunnel, Yan Dawu, the deputy general manager of the construction company, said at a news conference.

An evacuation was ordered, but water gushed in and 14 people were unable to get out, Yan said. “We feel deeply guilty and deeply blame ourselves,” he said.

The area where they were working is under a reservoir. By 12:30 p.m., rescue teams had plugged the hole where water was coming in. They were draining and pumping water from the reservoir as well as from the tunnel.

More than 1,000 workers, 22 fire trucks and five pumping vehicles were taking part in the effort, with search and rescue teams dispatched from surrounding cities in Guangdong province.

In March, two workers died in another part of the tunnel when a protective wall collapsed and they were hit by falling stones, according to a notice from the Zhuhai emergency management department.

Zhuhai is a coastal city near Macao at the mouth of the Pearl River delta. It was one of China’s early special economic zones when the ruling Communist Party started opening up the nation’s economy about 40 years ago.