Officials with Ottawa's transit provider say they're investigating an incident in which a bus driver allegedly walked off the job after a passenger asked why the bus was frequently late.

Commuter Henry McCambridge said an OC Transpo driver stranded him and 15 other riders on an idling bus at Ottawa's Mackenzie King station on Monday morning.

"He walked off and left the bus running," said McCambridge. "He left us abandoned, right there on the bridge."

OC Transpo, the bus driver's employer, has expressed regret for any inconvenience to customers and pledged to get to the bottom of the incident.

"We apologize to all customers who were on the bus when this incident happened," OC Transpo said in a statement emailed to CTVNews.ca.

Moments before the incident occurred, McCambridge said he had asked the bus driver why the No. 5 bus was consistently 40 minutes late.

When bus driver allegedly refused to answer the question, McCambridge said he turned to his fellow passengers and urged them to complain to city officials.

"When I turned around, the bus driver was putting on his coat and he was walking out the door, the bus was still running and he said ‘Get another bus,'" he said.

Passengers said they waited on the idling bus for about five minutes before deciding to leave. One rider was reportedly in a wheelchair and needed to be lifted off the vehicle by four fellow passengers.

McCambridge said the bus driver and an OC Transpo supervisor arrived about 20 minutes later. He said the two had a private meeting before the driver pulled away from the station with the empty bus.

The supervisor told riders that the bus driver had been "relieved of his duties" and was taking the bus back to the company garage where he would be "addressed by the management," said McCambridge.

While McCambridge said he still isn't sure why the No. 5 bus is consistently late, he said passengers should be a driver's top priority.

"It's deplorable," he said. "Maybe there's mixed feelings with the bus driver's union, the city — but we're not being held hostage."

The incident comes a little more than a week after an OC Transpo driver was caught threatening a disruptive passenger in an expletive-laden rant posted to YouTube.

OC Transpo general manager Alain Mercier said Monday that the company has fired the driver accused of the angry tirade.

Both incidents don't bode well for OC Transpo, which is currently trying to move on from a labour dispute that has unfolded over the past few months.

With a report from CTV Ottawa's Catherine Lathem