Police have spoken to staff at Edinburgh Airport as part of their inquiry into the conduct of former First Minister Alex Salmond.
It emerged in August that two women had made complaints to the Scottish government about Mr Salmond.
Airport bosses confirmed that they were "assisting police with inquiries" into a separate alleged incident understood to date from 2008.
The former first minister denies "all suggestions of misconduct at any time".
Police have declined to comment further.
The Scottish government set up its investigation after two formal complaints about Mr Salmond were lodged in January this year.
These are understood to relate to claims of sexual harassment while he was first minister, which he describes as "patently ridiculous".
Mr Salmond has launched a judicial review of the Scottish government's handling of the matter, claiming it was "unfair and unjust". The government insists its processes are "legally sound", and arguments about this will be heard in court in January 2019.
'Not been interviewed by police'
A separate police investigation into the claims was established in September, after the row over the government's inquiry became public.
This is a separate probe from the government one and will not be affected by the outcome of the judicial review.
The Daily Record newspaper reported on Monday that the probe had been widened to include an alleged incident at Edinburgh Airport.
A spokesman for Edinburgh Airport said: "We can confirm that we are assisting Police Scotland with its inquiries. We cannot comment further at this time."
A spokesman for Police Scotland said inquiries were continuing, and that police would not be commenting further.
A spokesman for the former first minister said: "Mr Salmond denies all suggestions of misconduct at any time and suggests that everyone should allow police inquires to take their proper course without briefing or breaching their confidentiality.
"Alex has not been interviewed by the police about any matter. He is content to have his case against the Scottish government stated in the Court of Session in January."