A fast-moving fire severely damaged an Aspen condominium complex early today, but speedy evacuation of residents prevented injury, authorities said.

"If it had been (reported) a few minutes later, we might have lost the whole building," said Rick Ballentine, deputy chief of the Aspen Volunteer Fire Department.

He said a passer-by called authorities about 1:30 a.m. to report the fire, which heavily damaged at least four of the building's units, which he estimated at a total of 10 or 12 units.

He said firefighters from Aspen and the Snowmass Wildcat Fire Protection District battled the blaze, which caused an estimated $1.5 million in damage.

The cause is under investigation.