Police Scotland are investigating claims Celtic striker Leigh Griffiths sent a girl under the age of 16 inappropriate messages.
Celtic are also looking into the matter and the 30-year-old has left the club's pre-season training camp in Wales.
Griffiths signed a one-year contract extension at Celtic last week and has made 261 appearances for the Parkhead club, scoring 123 goals.
A Celtic spokesperson said: "We have been made aware of online comments concerning Leigh Griffiths. The club will now look into this matter carefully.
"Leigh has left the club's training camp as we do this.
"It would not be appropriate to make any further comment at this time."
A Police Scotland spokesperson said: "We have been made aware of social media content. We are making enquiries and assessing for criminality."