More than 2,100 residents were being evacuated from the Air Force Academy's grounds Tuesday night as heavy smoke billowed from a wildfire that has burned an unknown number of homes near Colorado Springs.

The academy was telling families to leave two main housing areas, but an area of the 28-square-mile campus that houses cadets wasn't immediately evacuated. A new class of cadets is still scheduled to report on Thursday.

Fire officials had issued a pre-evacuation notice for the academy earlier Tuesday. El Paso County sheriff's officials have ordered an estimated 32,000 people to leave.

Fire information officer Greg Heule said earlier Tuesday that the fire was less than five miles from the southwest corner of the Air Force Academy's campus.

Television images showed homes burning and the Flying W Ranch southwest of the academy said on its website that the ranch had burned to the ground. Colorado Springs Fire Chief Richard Brown said "many, many homes" also have been saved.