URUMQI, Nov. 21 (Xinhua) -- An underground fire that has consumed more than 12.43 million tons of coal in northwest China has been extinguished after more than 50 years.

The Coalfield Fire Fighting Project Office of Xinjiang Uygur Autonomous Region announced the fire in the Terak field was finally out, saving an estimated 651 million tons of coal from burning.

Officials would closely monitor the coal seam for several years and submit a final report in 2009 to regional and national authorities, said Cai Zhongyong, deputy head of the office.

The fire, covering 923,500 square meters, was fueled by coal more than 100 meters underground. It released more than 70,000 tons of toxic gas, including sulfur dioxide and carbon monoxide each year since it started in the early 1950s, Cai said.

The project office took more than three years to fight the fire at a cost of more than 89 million yuan.

"First, we drilled into the burning coal bed and then poured water and slurry into it to lower the temperature," said Miao Pu, head of the fire fighting team.

"After the temperature dropped, we covered the surface to starve the fire of oxygen," said Miao.

Xinjiang, with estimated coal reserves of 1.82 trillion to 2.19trillion tons or 40.5 percent of China's total, has so far put out34 coalfield fires and plans to extinguish another 28 by 2015.

The local Coalfield Fire Fighting Project Office was established in 1958 to extinguish long-term coalfield fires plaguing the region.

Underground coal fires, most of which occur spontaneously, are common in the region's coal fields. Some fires have been burning for almost a thousand years and are technically very difficult to put out.

With an annual production of 50 million tons, Xinjiang is China's second largest coal producer after the northern province of Shanxi. Terak, 45 kilometers east of Baicheng County in southern Xinjiang, is the autonomous region's second largest coalfield. (One U.S. dollar equals to 7.415 yuan)