A TTC driver on the 165 Weston Road bus was photographed using a mobile device while driving Wednesday afternoon. (Courtesy of Mike Schmitz)

The Toronto Transit Commission is coming under fire after the emergence of a picture that shows a bus driver texting on a mobile device while apparently driving in the city's north end.

The picture was taken by TTC rider Mike Schmitz on his iPhone on Wednesday afternoon as he was riding on the 165 Weston Road North bus, which he says was in motion at the time.

"I think the photograph speaks for itself. We are very concerned about it," TTC spokesman Brad Ross told CBC's Metro Morning on Friday.

Ross said it was an isolated incident, and the TTC has begun an internal investigation.

"We will take appropriate action that is commensurate with the seriousness with which we view this public safety violation."

TTC chair Karen Stintz said in a Twitter post Thursday night that the "reported texting incident has upset me greatly. Safety is CRITICAL to Commission. #TTC Management will take appropriate action. Thank you."

'What did we warn you about!'

The TTC employees union, ATU Local 113, told its members on its Facebook page on Monday to "please avoid Facebook when [you] are on the job. Management is apparantly checking members who are commenting on here and the TIMES and checking if they are on duty when the timed posts are being posted."

In a posting Friday morning, the union said: "Look at the front of TheSun today and what did we warn you about!" That message was in reference to the photo, which was published on the front cover of the Toronto Sun Friday.

Ross said the TTC has a policy that prohibits the use of hand-held devices while operating a TTC vehicle.

"Aside from the fact that it's illegal, it is a policy violation of the TTC ... we take it very very seriously," he said.

In Ontario, it has been illegal to use hand-held devices while driving since October 2009 .

A driver caught in the act is subject to a fine of $155. Anyone challenging the ticket may have the fine lowered to $50 or raised to $500 at the judge's discretion.

Ross also urged riders who observe operators who appear to not be doing their job safely to contact the TTC directly.

"We don't want a repeat of last year where people were taking cellphone pictures and videos of our employees. That is not helpful."

Public anger at the transit agency reached a high last January when a picture of a TTC collector sleeping on the job went viral. Since that picture was published, the transit agency initiated a push to improve customer service.

Last year, it appointed a blue ribbon panel of outside experts who produced a number of recommendations on how to improve the rider experience.