JINAN, July 10 (Xinhua) -- Three rescuers died of heat stroke in fighting a coal mine fire on Sunday in east China's Shandong Province, according to the rescue headquarters of Zhaozhuang Fangbei Coal Mine.

The rescuers were obstructed by fire burning points under the mine shaft as they were scrambling to approach 28 miners who have remained trapped since the mine fire broke out on Wednesday.

A spokesman with the rescue headquarters said all of the three rescuers died of heat stroke because of working in high temperatures.

The rescuing teams progressed slowly, as the temperature in the mine shaft reached 60 degrees Celsius and exceeded 80 degrees in some areas, rescuers said.

A total of 91 people were trapped after an air compression device located in a parking lot 255 meters underground caught fire at 6:45 p.m. Wednesday. Sixty-three miners were rescued as of Thursday.

More than 1,000 rescuers have worked in rotation in the rescue operation.