Pictures have been released of the fire that has caused a halt to Dundee train services this morning.
The line between Dundee to Perth remains closed after a fire in a signal box at Longforgan.
Replacement buses are still transporting passengers between the cities as investigations continue.
ScotRail says 27 services are affected, with disruption expected for most of the day. Trains travelling from Aberdeen are terminating at Dundee, while services coming from Glasgow are only going as far as Perth.
Engineers from Network Rail are on-site to work on repairing the damage to cables.
UPDATE: The investigation is still ongoing, here's some pictures of the fire and the damage that it's caused. pic.twitter.com/VGgCubej9O
— ScotRail (@ScotRail) November 8, 2018
Fire crews were called to Longforgan around 1.30am.
One crew from the Macalpine Road station attended the incident.
A spokeswoman for the Scottish Fire and Rescue Service confirmed there had been a small electrical fire at the side of the railway line.
A spokesman for Network Rail Scotland said: “There was a line-side fire at around 1.30am which has damaged signalling cables near the box which is about 300ft away.
“We have engineers working to restore a full service for customers.”
A ScotRail spokesman said passengers could travel via Edinburgh instead, adding: “Services will restart when possible.
“We’re sorry to our customers who have been disrupted.”
According to Scotrail there was a blaze next to the track in Perth last night but there also reports of a fire in a signal box close to Longoforgan.
No trains to and from Glasgow Queen Street are calling at Dundee. Instead, a replacement bus is serving passengers between Dundee and Perth, where they can pick up trains to Glasgow Queen Street.
It is not known how long the disruption will last.
ScotRail tweeted at 6.21am: “Staff are on site and performing their investigation, after this an estimate will be given for repairs to be completed.”