Toronto police are warning the public after a high-risk sex offender convicted of crimes against children was released from prison on Thursday morning.

Investigators won't say what Toronto neighbourhood 30-year-old Junior Spencer will be living in, but say police will monitor his movements closely.

Spencer was imprisoned for sexually assaulting boys between the ages of 8 and 14 between 1995 and 2005.

The Correctional Service of Canada has labelled him a high-risk to re-offend.

Police have released a current photo and two past pictures that show Spencer's ability to change his appearance.

"If they're an offender and they do not have access to support, people who change their appearance can gain access to children and they can make themselves look different from what they do in any photograph," Det. Sgt. Gord Whealy, of the Sex Crimes Unit, told CTV Toronto.

"Typically, Spencer participates in grooming behaviour with the victims and their families, then exploits his position of trust to get access to the children," states a police press release.

"He has also volunteered with agencies dealing with children, again allowing him access to children."

Spencer is subject to a 10-year supervision order, which allows corrections officers and police to closely monitor his behaviour.