An independent investigation has been launched into the "culture" at ScotRail amid claims staff may have accepted gifts in exchange for contracts.
ScotRail declined to provide any details other than to confirm an investigation was taking place, but The Times understands the probe is focused on the property services management team, which looks after stations, depots, offices, shops and rented buildings.
An anonymous source told The Scotsman that a number of senior employees have been suspended while the investigation takes place, and that a car may have been involved as a "backhander" for a contract.
Scottish ministers have asked for an explanation and more information from the nationalised train operator.
Sue Webber, the transport spokeswoman at the Scottish Conservatives, said: “Taxpayers who are picking up the tab for SNP-run ScotRail will be keen for this investigation to be robust and thorough.
“This is a very serious situation and highlights an unacceptable culture that could potentially be operating within ScotRail.
“SNP ministers must come clean on how aware of this situation they are and what action they are prepared to take alongside the nationalised rail company to root this behaviour out.”
A spokesperson for ScotRail said: “We can confirm that an independent investigation is ongoing. We wouldn’t comment on individuals.
“We are unable to make any further comment until the investigation process has been completed.”