CARRBROOK, England (Reuters) - The army was called in to help battle a moorland blaze on Wednesday which has been spreading for days in hot weather near Manchester, northern England.

Soldiers will operate high-volume pumps and help move firefighters move across Saddleworth moor, Greater Manchester assistant chief fire officer Dave Keelan said.

“We have been liaising with a military adviser on the scene and ... have requested military assistance.” Keelan said.

The fire has been declared a major incident. Local schools were closed on Wednesday with residents advised to stay indoors and keep windows and doors closed. More than 100 firefighters and 29 fire engines are trying to bring the blaze under control.

But an improvement in air quality in the area allowed residents to return to some 34 houses that had been evacuated.

“There’s still a lot of smoke from the fire but air quality levels are being monitored regularly in different locations. Air quality is currently at a safe level and therefore residents have been let back into their homes,” Keelan said.

Like most of Britain, the area has experienced hot weather in recent days and forecasters expect temperatures to remain high for the rest of the week.

The cause of the blaze has yet to be determined.