An arrest warrant has been issued for an inmate who was mistakenly released from a southwestern Ontario detention centre disguised as his cellmate, police say.

Justin Kunz, 19, of London, Ont., left the Elgin-Middlesex Detention Centre (EMDC) on Wednesday. According to police, he "altered his appearance" to look like his cellmate, who was set to be released from custody.

Police said in a news release Thursday that Kunz was released under his cellmate's name.

"It is alleged that the inmate, Justin Kunz, altered his appearance to look like his cellmate who was about to be released from custody, threatened the cellmate to be quiet when the Correction Officer came for him, then identified himself as the cellmate when the Correctional Officers arrived," London Police Service said in the statement.

Kunz remained at large Thursday evening.

According to Ontario’s Ministry of Community Safety and Correctional Services, Kunz’s exit is not considered an escape, but an improper release.

"The ministry can confirm that inmate Justin Kunz was improperly released from custody," the ministry said in a statement on Thursday. "Contrary to reports, the inmate did not escape and to date no one has ever escaped on their own or with the help of others from the EMDC."

Kunz is now wanted on a number of charges related to the incident, including personation and uttering threats. Prior to leaving the EMDC, Kunz was being held in custody in connection to a number of offences, including possession of firearms and mischief.

Anyone with information is being asked to contact London Police Service at 519-661-5670, or Crime Stoppers at 1-800-222-TIPS (8477).