Rail passengers have been warned to expect major disruption to services on the Central Belt until at least 9am on Thursday morning.
The assistance loco is believed to be on site now to remove the broken down freight train.
Bus services are currently operating at Shotts, Haymarket and Livingston.
In a statement, ScotRail said:” There is a broken down freight train at Curriehill which means we are unable to operate a full train services between Glasgow Central and Edinburgh via Shotts. The assisting loco is now at the broken down train and we will update when we have more information.”
Customers can also use their valid ticket/SMART card on Lothian buses and First Bus services.
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