Six people died and three were seriously injured after a blaze broke out during construction work at a liquefied natural gas terminal in Beihai, Guangxi Zhuang autonomous region, local authorities said on Tuesday.

The fire started around noon on Monday and has been extinguished. The regional health commission has sent experts to help treat the injured.

The regional government vowed to discover the cause of the accident and strengthen supervision on construction safety to eliminate hazards on other sites.

The LNG terminal at Tieshan Port, the first in Southwest China, began trial operations in 2016 with an annual storage capacity of 6 million metric tons. It is operated by a subsidiary of China Oil and Gas Piping Network Corp, also known as PipeChina.

PipeChina said the subsidiary had expressed grief over the death of the workers and would pull out all stops to treat the injured and deal with the aftermath of the blaze.

The subsidiary said the fire broke out when the workers tried to examine and repair an LNG tank. It has suspended all construction work and said it will strengthen safety management.

Further investigation is underway to ascertain the cause of the accident.

In Lanzhou, Gansu province, a similar accident occurred on Tuesday morning when an oil tank at a chemical plant exploded and caught fire. The tank was used to store naphtha, an intermediate product in the petrochemical industry. No casualties were reported after the fire was extinguished, and an investigation into the cause of the explosion is underway, the local government said.

Shi Ruipeng contributed to this story.