For the second time in a week, Calgary police are reminding people how to recognize legitimate police traffic stop procedures after several reports of individuals impersonating police officers.

On Friday afternoon, a man driving northbound on Sarcee Trail N.W. pulled over at 16th Avenue N.W. after he heard a siren from a white vehicle driving erratically behind him. He later told police he noticed a flashing red light on the car's roof.

Two men got out of the white car and asked the driver to exit and open his trunk. When the man asked to see the pair's police identification, they said they were letting him off with a warning and fled in their vehicle.

Police said Monday they're looking for two Caucasian men about 18 to 20 years old with slim builds, driving an older-style, white, four-door car with tinted windows that could possibly be an Oldsmobile.

Although the victim was not threatened, police said they believe one of the men might have been armed with a gun.

Last week, two Calgary males were charged with impersonating a police officer after the pair tried to pull over three young women in Hidden Valley.

Calgary police reminded the public that officers are required to carry identification at all times and that drivers have the right to ask to see it.

Traffic stops are done with marked vehicles equipped with red and blue lights on top or unmarked vehicles driven by police officers in full uniform, said Staff Sgt. Jim Rorison. Plainclothes officer use unmarked vehicles with red and blue strobe lights located inside the grill or vehicle interior.

If a driver is unsure about a vehicle that's pulling them over, they should call 911, Rorison said.