The mystery behind the lights which appeared over WA skies early this morning has been solved. The Perth Observatory says the lights were caused by a meteorite building up in the atmosphere.

Coloured lights could be seen in the sky from Bunbury to Geraldton around 5.30am.

Residents contacted the Observatory and the WA Water Police, looking for answers.

They described the colours of the lights as green, white and yellow.

Perth Observatory technical officer and astro-photographer Richard Tonello said the green flashes were a tell-tale sign of a meteorite.

"The same thing happened in November 2005 from Augusta to Lake Grace," he said.

The lights were about 100km above the surface of Earth.