The NBA is investigating the Philadelphia 76ers over whether they may have committed a violation of the league's new Player Participation Policy due to James Harden's absence in Thursday's game.

Harden remained in Philadelphia ahead of the Sixers' regular season opener at the Milwaukee Bucks.

"We're looking into the facts around James Harden's availability tonight to determine whether an approved reason exists for his lack of participation," said league spokesman Mike Bass in a statement.