A fireball lit up the skies of western South Dakota and Nebraska and of eastern Colorado late the night of Jan. 11, but authorities have not determined what it was, reported Associated Press and the Rapid City Journal.

Some speculated that it was the Russian space station Mir, but this was disputed.

Motorists traveling Interstate 80 about 9:30 p.m. first reported seeing a blue flash of light drop to the horizon.

Similar reports were made at several points in Nebraska’s Black Hills and in the Denver area.

Reports varied as to the colour of the fireball. Three eyewitnesses said they saw a bright-green fireball falling to the horizon in * the southern sky. Others said the light was “whitish-blue.”

One man reported seeing a fireball the ‘ size of a pickup truck falling in the sky.

“It was a flash the size of the moon, possibly smaller,” said another witness. “It was moving rapidly toward the horizon. It was not a plane or a fire. It was very brilliant green in colour.”

Another witness said he “saw a really bright light… It was the biggest one I ever saw. As it went south toward the ground, it had a large glow like an explosion.”

A Nebraska motorist said the ball of light appeared to drop near an airport: “That’s how close it seemed, but it could have been far off.”

Police said there was no evidence of a meteorite in the area.

A helicopter emergency medical technician also saw it: “It was just a big bright burst of light, then it just burned itself out.”