TransLink is blaming an unspecified computer problem for halting service on the Expo and Millennium SkyTrain lines during rush hour Thursday.

The issue started around 5 p.m. and initially caused both lines to shut down completely. Limited service resumed around 5:50 p.m. but it wasn’t until after 8 p.m. that the system was fully restored.

On Thursday evening, TransLink executive Fred Cummings issued a statement apologizing for the lengthy delay, which trapped hundreds of riders on muggy trains and caused huge crowds to build at stations across Metro Vancouver.

“We apologize to our customers for this unusual incident,” Cummings said.

“We know it can be very frustrating as it affects their ability to get where they need to go, especially during rush hour. Our people worked as quickly as they could to look after our passengers who were affected.”

When the disruption started, several trains ended up stopped between stations.

A small handful of passengers, apparently frustrated being trapped in the heat, forced train doors open and tried to walk away along the guideway.

Cummings said those riders inadvertently triggered an automatic system-wide hold, causing further delays.

Attendants were eventually able to manually drive the trains to nearby platforms, though it took until 6:45 p.m. – almost two hours after the issue arose – to get the last passengers offloaded.

TransLink also set up bus bridges between SkyTrain platforms to help deal with crowding and lack of service.