Police said someone tried to rob a Pharmaprix store near the corner of Sherbrooke and Hogan streets around 10 a.m. Tuesday.
Officers nearby gave chase and followed a suspect to a small apartment building across the street.
A tactical team is on site and officers are trying to make contact with the suspect.
No injuries have been reported.
Police are telling people to avoid the area on Sherbrooke Street between Bercy and Montgomery streets.