Police have found a fly screen in the investigation into the sexual assault of a seven-year-old girl in her home in Ellenbrook.

The child woke on Monday morning and told her parents she had been sexually assaulted in her bedroom overnight.

Mounted police and forensic investigators have been combing the area as the hunt continues for the intruder.

Detectives had been looking for a fly screen removed from the house, although they are still searching for a child’s navy blue Christmas-themed T-shirt.

Detective Inspector Hamish McKenzie says it was a heinous and disturbing crime.

“We have had some developments overnight in that we have located the fly screen that we have been searching for in the search area, so that’s a particularly pleasing development for us, and that is being forensically tested as we speak,” he told 6PR Breakfast.

“At present we would just ask the general public just to look out for the blue t-shirt, the Christmas t-shirt … if they can keep an eye out for that t-shirt, because that is still outstanding and we are very keen to locate that, because it may provide some evidentiary value for us.”

Detectives are appealing for information from members of the public who may have dash cam or CCTV footage in the area.

Press PLAY below to hear the latest on the investigation

Images: Nine News/WA Police