Network Rail engineers are working to repair a section of the line between Kilmarnock and Barassie after a large hole appeared close to the tracks.
The unusual void was identified on Saturday June 4 and Network Rail is working with experts from the Coal Authority to investigate potential mineworkings in the area.
An exclusion zone has been set-up around the site while expert engineers confirm the cause of the hole, as well as its full size and depth.
Those investigations will then allow Network Rail engineers to plan a programme of repairs, as well as giving a clearer indication of when the line can re-open for passengers.
The line is expected to remain closed for a number of weeks due to the potential complexity of the repairs needed to stabilise the mineworkings beneath the track.
In the meantime, services between Kilmarnock and Barassie will remain suspended with a replacement bus service in operation.
Trains between Ayr and Girvan/Stranraer, and between Glasgow Central and Kilmarnock will operate as scheduled.
Tom Podger, Project Manager for Network Rail, said: “Holes like this are very unusual on the railway and we’re working with the Coal Authority to identify the cause, as well as finding a solution to make the railway safe for trains to pass again.
“We understand the inconvenience this incident will cause to some passengers, and I’d like to thank those customers for their patience and understanding while work continues.”
Passengers can check their journey at https://www.nationalrail.co.uk/ or https://www.scotrail.co.uk/.
Photo credit: Network Rail