Hundreds of fire-fighters were struggling to control a fire spreading in the virgin forest in southwest China's Tibet Autonomous Region, said local sources on Friday.

Thick smoke was spotted around 6 AM. Thursday at a forest in Bomi County of Nyingchi Prefecture in Tibet's southeastern area.

Strong winds had made it difficult to curb the spread of the blaze, according to the fire-fighters.

Damage caused by the forest fire cannot be calculated at the time, but no casualties have been reported.

The cause of the fire is under investigation.

Tibet experienced its third warm winter in the last seven years, with a temperature rise of nine degrees on the average in some areas.

Tibet reported an average temperature of minus three degrees Celsius between December 2006 and February 2007, up 1.4 degrees from the historical average of minus 4.4 degrees Celsius, according to the regional meteorological bureau.

Meanwhile, most parts of Tibet reported a 50-percent decline in rainfall, which measured less than one mm at 17 of the region's 32 meteorological stations between early December and the end of February.

On April 20, a fire broke out in a forest four km from the Bayi township, also in the Nyingchi Prefecture.

The fire was extinguished in two days by more than 6,000 fire-fighters after an artificial rainfall operation was performed.

The warm and arid climate was to blame for several forest fires in Nyingchi and would increase the risks of plant diseases and insect pests in the summer, meteorological experts said.

(Xinhua News Agency May 5, 2007)