Police are assessing an allegation that Celtic striker Leigh Griffiths sent inappropriate messages to a second teenage girl on social media.
Griffiths was sent home from Celtic's pre-season training camp earlier this week after officers began a probe into online activity.
Celtic are also investigating claims that Griffiths sent inappropriate messages to a 15-year-old girl on social media.
It is understood the new allegation relates to another teenage girl.
A Police Scotland spokeswoman said: "We are aware of the social media content and the matter is currently being assessed."
After claims were first made on social media, Griffiths did not feature in Ange Postecoglou's first friendly game in charge of the club as Celtic beat Sheffield Wednesday 3-1 in Newport on Wednesday afternoon.
A Celtic spokesman told several media outlets later that day: "We have been made aware of online comments concerning Leigh Griffiths. The club will now look into this matter carefully.
"Leigh has left the training camp as we do this. It would not be appropriate to make any further comment at this time."
Celtic took up a one-year option on the 30-year-old striker's contract last week after his Parkhead future had been in doubt.
Sky Sports News has contacted Celtic for comment.