Montreal police alerted the Toronto Police Service to possible corruption within its drug squad back in 1997, but the red flag was ignored, newly obtained internal documents show.

The now-defunct group of drug squad officers was at the centre of a massive police corruption probe, following complaints from drug dealers that prompted an internal investigation carried out by a special task force.

CBC News and the Toronto Star obtained a 2004 Montreal police document that reveals the force informed Toronto police they were concerned after a "suspicious" encounter with a pair of drug squad officers in 1997.

According to the document, the officers from Toronto appeared to be intent on obtaining cash from a suspect's safety deposit box.

Seven years later, charges were laid against six drug squad members for allegedly robbing drug dealers.