A massive fire caused by an explosion at oil pipelines at a busy port in northern China has finally been extinguished after burning for 15 hours.

The explosion at one oil pipeline triggered a smaller pipeline to explode near Dalian's Xingang Harbour.

More than 2,000 firefighters worked through the night to control the flames and further explosions on the second pipeline.

The pipelines are owned by the state-owned China National Petroleum Corp., which is Asia's biggest oil and gas producer by volume.

Officials said that firefighters have turned off valves on all oil tanks at the site. But environmental protection officials told China National Radio that the scene remained unsafe because of the dense chemicals in the air and large chemical tanks nearby.

No casualties were reported, a city government spokesman said.