HOHHOT, May 2 (Xinhua) -- Firefighters have put out a fire that extended from Russiato primeval forest in Inner Mongolia Autonomous Region, north China, authorities said Tuesday.

The fire started in Russia and spread across the border Sunday afternoon to Yimuhe forest in the northern Greater Hinggan Mountains, according to local forest administration, adding that the cause of the fire is under investigation.

More than 1,300 firefighters and police had extinguished the fire by 11:21 p.m. Monday. Steps are now being taken to prevent the fire reigniting, according to the administration.

This spring, the temperature in Inner Mongolia is 1 to 2 degrees Celsius higher than the average over previous years, increasing the fire risk as the region's forests are particularly dry.