Dundee United will investigate "thoroughly" claims that defender Mark Connolly breached Covid-19 regulations.
It was reported the 28-year-old refused to wear a face covering when travelling in a taxi during a night out in Dundee earlier this week.
It comes less than a week after nine Scottish Premiership players were punished for quarantine breaches.
"This is an internal matter and we'll be investigating it thoroughly," a spokesman said.
"The club will make no further comment at this time."
On Friday, Celtic's Boli Bolingoli was given a three-game ban - with a further two games suspended - for travelling to Spain, then failing to self-isolate.
And eight Aberdeen players - Bruce Anderson, Craig Bryson, Sam Cosgrove, Michael Devlin, Jonny Hayes, Matty Kennedy, Dylan McGeouch and Scott McKenna - received suspended three-game bans for visiting a bar on 1 August.