Regulators fined the San Francisco Bay Area transit agency (BART) for safety failures associated with an incident five years ago which killed two workers inspecting a track during a union strike.

Two workers were killed in 2013 when they were inspecting a track and were struck by a train, and at the time there was a worker strike, so the agency was working to restore an already limited service. The train that struck them was a training exercise to teach managers how to drive in case of a prolonged worker walkout. The trainee who was driving the train had no direct supervision in the cab, and he hit the emergency brake and tried to hit the button for the train’s horns but hit the button that controlled the doors.

The California Public Utilities Commission put BART on three years of probation and said that the fine would double if BART committed any safety violations during that period.

BART spokeswoman Alicia Trost said that they were reviewing the decision. Last year a judge had ordered a $220,000 fine last year which the agency appealed to the five-member commission.

Commissioner Liane M. Randolph said the fine had been increased because of the “egregious” nature of the safety failures and Bart’s response to the investigation was inadequate. BART was over 16 months late producing their accident report and their corrective-action plan was submitted four years after the accident, only two pages long.

Trost said that BART spent $2 million upgrading their safety barrier and plans to spend another $4 million in improvements, they have overhauled their safety policies since the accident. At the time of the accident BART was using a “simple approval” safety procedure that trusts track inspectors to be responsible for their own safety and determined that they could clear the track within 15 seconds of an approaching train if they need to. That policy has now been eliminated, and trains are required to stop if a worker is within 6 feet of the track.

BART was fined $214,000 in 2014 and paid one of the worker’s families in a wrongful-death lawsuit and settled a workers’ comp claim with the other worker’s family.

Read more from the Associated Press.