Police are scouring a Richmond Hill park for evidence after a teenage girl was approached by a man wearing a ski mask and sexually assaulted.

It happened at approximately 12:30 a.m. Thursday. York Regional Police say the young woman had just exited a bus, and was walking across the street when she was approached by a man.

The suspect was wearing dark clothes and a grey ski mask at the time.

Police say she was sexually assaulted in Toll Bar Park, located in the Canyon Hill Avenue and Yonge Street area. She was taken to hospital for treatment. Police have not provided further details on her condition.

On Thursday, officers were at the park searching for evidence, including anything the suspect or victim may have dropped.

"If anyone was in the area and might have seen someone wearing a grey ski mask, anywhere from 11 onwards in the evening or until right after the assault took place…please contact the York Regional Sex Assault Squad," Const. Andy Pattenden told CTV Toronto.

With a report from CTV Toronto's Janice Golding