BEIJING/Dalian - China National Petroleum Corp (CNPC), the country's largest oil and natural gas producer and supplier, said a weekend fire at its refinery in the coastal city of Dalian has been contained without casualties or environmental damage.

Firefighters work to quench a blaze on Saturday at a refinery of China National Petroleum Corp in Dalian, Liaoning province. The fire is reportedly contained with no known casualties. Cai Yongjun / for China Daily

The blaze, which started at 2:25 pm on Saturday, was extinguished and brought under "complete control" without causing any environmental damage, according to a statement on the company's website on Sunday. The fire was extinguished by 7:57 pm the same day.

"A comprehensive offshore environmental evaluation was started to monitor the water quality, and no pollution has been detected in the nearby sea area so far," Qi Xiangyang, director of the press information office at the Dalian Oceanic and Fishery Administration, told China Daily on Sunday.

The fire was caused by a leak from a valve, according to CNPC, but the reason for the leak is still under investigation.

A local resident surnamed Shang, who witnessed the incident, told China Daily on Sunday the facility underwent repair and maintenance in June and there was a banner hanging in the facility announcing the plant's safety record in June.

"More than 60 fire trucks arrived at the scene, but it is only a small incident compared with the crude oil pipeline blast at a CNPC terminal in Dalian's Xinggang port in July 2010," Shang said.

Although officials and the company said no environmental damage had been detected so far, environmentalists expressed some skepticism about the assessment.

An environmentalist surnamed Li at the Dalian Environmental Protection Volunteers Association said due to recent strong winds in Dalian, it is hard to tell if the incident polluted the environment nearby.

A homebound commuter on a bus that passed the plant told China Daily that upon witnessing the fire and heavy smoke, passengers called their homes to tell family members to shut the windows and doors and take laundry inside.

On Sunday afternoon, almost an entire day after the incident, a China Daily reporter was unable to observe any smoke or fire.

"Small incidents often happen around the facility," Shang said.

A CNPC oil pipe exploded at the Dalian port exactly one year earlier. The explosion caused a fire, and about 1,500 tons of oil leaked into the sea.