A fireball with a long tail of green, orange and purple flames raced across the sky over southwestern Colorado around 7:30 Sunday night. A scientist and a military spokesman said it was probably a meteor.

Authorities in several counties got reports from residents saying it had a 500-foot tail and it was huge, like a meteor. Astronomer Larry Esposito said a meteor falling could be enough to surprise a lot of people.

A professor at the University of Denver estimated the meteor as being baseball-sized, and he believes it may have burned up on entering the Earth's atmosphere.

North American Aerospace Defense Command spokesman Major Ed Thomas says no man-made objects fell from space Sunday. NORAD tracks satellites and thousands of pieces of space debris.

Police and the media report "hundreds" of telephone calls in the Denver metro area and as far west as Salt Lake City.