Rocket propellant stored in a munitions igloo at Hill Air Force Base ignited and burned Monday afternoon, causing some property damage and a grass fire but no injuries, according to a base spokesman.

The fire, which ignited and burned as much as 40,000 pounds of rocket propellant, started about 1:30 p.m. in Building 1825 on the base. It was described as "rapid burning," although there was no explosion, said Lt. Col. Bruce Rianda, deputy commander of the 2849th Air Base Group. At one point, the igloo's doors opened, causing grass around the building to be ignited.After the fire was extinguished, a 2,000-foot area around the igloo was cordoned off for safety reasons, including the Roy gate into the base, which also serves as entrance to the Hill Air Force Base Museum. That entrance will be closed until noon Tuesday, the base spokesman said.

An initial investigation showed there was no one in the igloo when the fire broke out and no injuries reported. The fire's cause is being investigated.