MONTREAL -- Montreal police officers responded after 911 calls reported shots being fired on Notre-Dame St. near St. Francois Xavier St. in Old Montreal.

Officers arrived shortly after 3:10 a.m. and found shell casings in the area, but were unable to locate any impact marks.

The officers spoke to witnesses, who saw men fleeing the scene quickly in a car.

Officers located the car around Bridge St. and Wellington St. and saw three men flee on foot.

Two 23-year-old men and a 29-year-old man were arrested, while the driver of the car fled in the vehicle and remains at large. The men were released without being charged, and the investigation is ongoing.

With the help of a K-9 team, officers located a firearm and are performing tests to see if it matches the shell casings.

Preliminary investigations suggest that the shots were fired in a conflict between two groups of people.

No one was injured in the shooting.