Southern District Police are investigating an alleged sexual assault in Seaford Meadows.

Between 2am and 4am, Wednesday 9 February, a 17-year-old girl was approached by a man on a yellow motorcycle at a park off Derrick Street and sexually assaulted.

The suspect is described as being Caucasian, 20-30 years of age with a shaved head and facial stubble. He was wearing a white t-shirt, a black zip-up top, jeans and a black cap underneath black motor cycle helmet.

Anyone with information about this incident or may have seen a motorcycle or heard anything in the vicinity of the park is asked to call Crime Stoppers on 1800 333 000 or online at www.crimestopperssa.com.au