Transport authorities are investigating how a power failure stranded passengers on trains stuck across the Sydney Metro.
Two commuter-laden trains were stuck on the tracks on Monday for almost an hour without power, meaning no air conditioning or lights.
The incident sparked massive delays along the line as services returned to normal about 9.40am.
A Sydney Metro spokeswoman said a power failure on the Metro North West Line caused emergency brakes to fire.
Operators were unable to release the brakes remotely so a technician was sent to manually reset them.
"Unfortunately this resulted in significant delays across the network. We apologise for the inconvenience," the spokeswoman said.
"Sydney Metro will investigate the cause of delays and the impact on passengers with the operator, Metro Trains Sydney.
"The delay in disembarking passengers is not acceptable."
The two trains with commuters were eventually moved to the closest platform where passengers were able to disembark.
