The funicular railway started running in 2001
The funding of the mountain railway in the Cairngorms looks set to be investigated by the public spending watchdog Audit Scotland.
Public development agency Highlands and Islands Enterprise (HIE) subsidised the building of the funicular.
But due to long-running financial difficulties HIE stepped in to take over ownership of the operating company from CairnGorm Mountain Limited.
This agreement involved wiping out its accumulated debts.
Auditor General Robert Black has submitted a report to the Scottish Parliament to say he wants HIE's funding of the funicular to be reviewed.
The Cairngorm ski resort and railway were taken over by HIE in May.
It follows agreements reached with Bank of Scotland Corporate and CairnGorm Mountain Trust on large debts owed by CairnGorm Mountain Limited (CML).
Highland Council had previously agreed to write off a £1m loan to CML.
The running of the mountain railway, which started operating in 2001, was expected to be put out to tender.