A fireball that blazed over the Rockies earlier this month was not a meteor or other celestial body, experts have said.

People from New Mexico to Montana saw the bright object break apart as it moved slowly northwards across the night sky. More than three dozen witnesses filed reports about the unusual sighting, described as three "rocks" with glowing red and orange streaks, which happened at 10.30pm local time on September 2.

But it was probably part of a Russian spy satellite that fell from orbit and burned up over Colorado and Wyoming, experts said. The object was most likely a piece of Russia's Cosmos 2495 reconnaissance satellite, launched in May, said Charles Vick, an aerospace analyst with military information website Globalsecurity.org.