Toronto Police are investigating reports that an 18-year-old woman was sexually assaulted early Friday at York University.

The incident happened during a frosh event just after 1 a.m. at a large dance party held at the Stong residence.

Police say the woman was approached from behind and assaulted. She was not injured.

The suspect is described as 18 to 20 years old, between five foot two and five foot seven inches tall and weighing between 150 and 160 pounds.

He has an olive or tanned complexion and a piercing on his lower lip.

He was wearing a black zip-up hooded sweatshirt with a brimmed hat underneath.