Trains through Perth and Fife were cancelled after a signalling problem caused “major disruption” on the route on Thursday.
ScotRail said the issue was discovered at Ladybank just before 6am.
As a result, several services between Perth and Edinburgh were cancelled.
Services for Glenrothes and Dunfermline also affected
Engineers were called to the scene and had fixed the problem by around 8am.
In an update just before 8am, ScotRail posted on Twitter: “Engineers have now fixed this issue and we’re able to run trains through this area again.
“We’re working hard to get services running back to schedule.”
Passengers quiz ScotRail bosses
The disruption came after passengers quizzed ScotRail bosses on Wednesday night about services across Perthshire and Fife.
The operator admitted the link between Perth and Edinburgh was “not competitive” with other forms of transport.
It comes ahead of proposed timetable changes in May next year, which could see about 300 services cut across the country – a move many staff members feel will negatively impact on passengers.