Montreal police are dealing with a major breach of confidential police information and say retrieving it is a top priority.

CTV has confirmed that a bag belonging to a high-ranking police officer was stolen from his unmarked car on December 17, 2015.

Commander Patrice Vilceus, who heads the Eclipse squad that investigates organized and violent crime, was at a Christmas party when someone broke into his car.

The thieves stole a bag which contained a USB key that held contact information for police informants, and classified information about an ongoing police investigation.

Some are wondering if the theft of the USB key is linked to five shootings that happened in Montreal the week after. The shootings, which police have said could be related to street gangs, left one man dead and four others injured. But police deny there is any link between the theft and the shootings.

High-ranking organized crime investigators have been searching for the memory stick but police will not make any other comment about the case aside from saying it is a serious privacy breach which could have drastic consequences.

This is not the first information breach the Montreal police have had to deal with. In 2014 organized crime investigator Benoit Roberge was sentenced to eight years in prison for selling classified information to the Hells Angels.

A few years earlier a retired veteran of the Montreal Police force, Ian Davidson, stole and then tried to sell a long list of police sources to organized criminals.

Davidson was arrested at the time and then committed suicide.