Swindon Town have suspended three of their players and are investigating reports they inhaled nitrous oxide on a live social media video on Wednesday.
Images appeared to show Drissa Traore, Brandon Ormonde-Ottewill and Jeremy Balmy taking the legal high, commonly known as laughing gas, via balloons.
"The club have already started an internal investigation into the trio's recent conduct," a club statement said.
"They will not be considered for selection during this process."
The Robins, who are 15th in the table, lost 2-0 at Oldham Athletic on Tuesday.
Swindon have not won in six games since head coach Luke Williams signed a five-year deal on 9 March, following a run of six wins from 10 in interim charge.
Between 2006 and 2012, 17 people in the UK died after taking nitrous oxide.
A new law designed to crack down on legal highs was due to come into force but has been delayed.
Then-Liverpool boss Brendan Rodgers said he would speak to England forward Raheem Sterling, now at Manchester City, after he was pictured allegedly taking nitrous oxide in 2015.