A technician triggered an emergency fire system leading to a breakdown in Metro services that left passengers stuck on their morning commute.

The services between Chatswood and Tallawong stopped running about 9:30 Monday morning due to a “communications system issue”.

A listener tells Ray Hadley his wife was stuck on the metro from Castle Hill to Macquarie for 40 minutes before the passengers were moved on to the replacement buses.

The 12-minute journey took her almost two hours.

NSW Transport Minister Andrew Constance tells Ray a technician “accidentally broke the glass” of the fire suppressant system in the equipment room at Tallawong which released gas, sucking the oxygen out of the facility.

The system was affected and the trains automatically stopped while the facility was evacuated.

Ray Hadley questions how this could occur.

“I’d imagine you’d have to use some force to ‘break glass in case of fire’, how does someone accidentally break one?”

The Minister admits he is not sure.

“I’ve got no idea, that’s what we need more information on.

“Someone’s obviously been careless… but they will get to the bottom of how he’s managed to break the system.”

Click PLAY to hear the full interview

The services are now running again.

Image: Getty/ Matt Blyth