CEO Andy Byford on Thursday announced in a letter to employees that Sameh Ghaly and Andy Bertolo have left the organization amid a "change of leadership" in the TTC's Engineering, Construction and Expansion Group.
Bertolo was the chief project manager of the expansion, and worked under Ghaly who headed the EC&E Group.
According to a report in the Toronto Star, the unfinished 8.6-kilometre subway extension from Downsview Station to York University and beyond is approximately $400-million over budget and possibly two years off-schedule.
The TTC has recently come under pressure from Mayor John Tory and TTC chairman Josh Colle to rein in spending and get the subway expansion back on track.
Colle has disputed the $400 million figure, but recently said the project's actual overrun is not known.
Byford said he will outline the project's next steps following a TTC board meeting on March 26, at which he said a report outlining options for a revised schedule and budget will be presented. That report will be made available to the public on Friday.