A railway line has been closed after a train derailed during overnight testing.
The incident happened near to Dalwhinnie station in the Highlands at around 3.15am on Saturday.
ScotRail said it was not a passenger service and no one was injured.
It is not yet known how long it will take to recover the train and reopen the line.
Network Rail will provide information and updates where possible.
Passengers have been warned to expect disruption to services.
Trains travelling north will go as far as Pitlochry in Perthshire and restart from Aviemore in the Highlands, while southbound trains will stop at Aviemore and restart at Pitlochry.
A ScotRail spokesperson said: “Services between Perth and Inverness are currently disrupted, there will be replacement bus services for those making essential journeys.
“Customers should check our website, app and social media channels for the latest arrangements before they travel.”