Another day, another incident involving one of OC Transpo's double-decker buses.

On Wednesday afternoon, motorists spotted what appeared to be smoke coming from a double-decker bus travelling west on Highway 174 near Blair Road.

Troy Charter, the city's director of transit operations, initially said a coolant leak, not fire, was the cause of the smoke.

He later said the smoke was actually steam.

"There was no fire," Charter said in an email. "The bus will be towed back to a garage for repair."

Less than 48 hours earlier, however, one of OC Transpo's double-decker buses did catch fire during Tuesday morning rush hour at Queensway station.

The City of Ottawa said all passengers got off that bus safely, but an OC Transpo special constable who was helping with the evacuation suffered minor smoke inhalation.

The safety of OC Transpo's double-decker bus fleet has been a matter of public concern ever since three people died and 23 people were injured when one of the buses collided with the shelter at Westboro station on Jan. 11.