Sex assault of Qld girl being investigated

Police have described the sexual assault of a girl on Queensland's Mornington Island as serious.

Four males are assisting detectives investigating the incident which occurred last week in the Gulf of Carpentaria, Queensland police said on Thursday.

"We're not going into much more detail because Mornington Island is a small community," a police spokesman told AAP.

The girl is being treated in a north Queensland hospital and is in a stable condition.