An extensive search is underway for a missing girl who was last seen swimming in a creek in the Lambells Lagoon area at around 5:30 pm this afternoon.

The girl who is approximately 12-years-old, was swimming with three other children when she went underwater and did not resurface.

The three children walked to a nearby house and notified one of their parents who called police shortly before 6pm.

The children told police that they saw a crocodile in the area.

The Territory Response Section has cordoned off Lambells Lagoon and is coordinating the search efforts.

The girl is described as Caucasian, with black straight shoulder length hair and was wearing brown board shorts and a green and blue coloured bikini top.

Due to heavy rain, the poor visibility and a crocodile sighting, Police are advising members of the public to avoid the area for safety reasons.