Championship leaders Burnley being investigated for playing weakened side against relegation rivals of Huddersfield Town and Rotherham United
Fresh from securing promotion to the Premier League, the Clarets made several of changes in the match at the Madejski Stadium, with the relegation-haunted Royals picking up a valuable point.
Their line-up has angered Huddersfield Town, according to reports.
It is claimed that the EFL have written to the Clarets over the matter. If found guilty, they could face a potential points deduction and a fine.
Burnley - who lost at home to struggling QPR on Saturday in a shock reverse, remain adamant that changes to the line-up were only made to work around their hectic schedule.
Their previous game was against second-placed Sheffield United five days earlier. Their following game was at Rotherham United last Tuesday.
Goalkeeper Bailey Peacock-Farrell, defenders Charlie Taylor and Ameen Al-Dakhil, midfielder Scott Twine, and forwards Manuel Benson and Lyle Foster were all selected at the expense of Aro Muric, Taylor Harwood-Bellis, Ian Maatsen, Jack Cork, Josh Brownhill and Ashley Barnes. Brownhill was injured.
Huddersfield and Rotherham, who lost at Bristol City on Saturday, remain embroiled in the survival fight and face crucial games in the next seven games against fellow strugglers Cardiff City.
Town host Reading on the last day of the season.
They are one point clear of the third-from-bottom Royals, with a game in hand.