ORLANDO, Fla. -

A mysterious sight in the sky prompted numerous reports of UFOs, and the cause of the sightings took place in South Florida.

The Air Force says it received reports Wednesday night from Jacksonville to the Florida Keys about a weird, bluish cloud.

Many residents also called the National UFO Reporting Center.

Scientists say, however, that the sighting was not a UFO but instead was caused by exhaust fumes from a Delta IV rocket. During the launch, ice crystals formed in the sky, causing the confusion, scientists say.

The same phenomenon occurred in South Florida in 2009 after a shuttle launch.