Arsenal say they are taken allegations that France striker inhaled nitrous oxide "seriously".
Alexandre Lacazette could face disciplinary action from Arsenal after footage emerged of the striker seemingly inhaling from a balloon.
The Daily Star posted a video of the France striker appearing to inhale with a balloon to his mouth, claiming he was using nitrous oxide.
It is alleged that the 28-year-old wrote in a text to friends "at home, chilling and doing balloons”.
Lacazette was among a group of Arsenal players who were warned by the London club 18 months ago after they were seen taking in nitrous oxide at a London nightclub.
The former Lyon forward looks set to have more questions to answer as the Premier League side wait to discover if and when the season can resume, having been on hiatus since March due to the coronavirus crisis.
An Arsenal spokesperson said: "This is a private matter which we are taking seriously. It will be handled internally."
Lacazette has scored nine goals in all competitions this season.