Dejounte Murray NBA Investigating Hawks Star ... After Bumping Ref

The NBA is investigating Hawks star Dejounte Murray for making contact with an official at the end of Game 4 against the Celtics Sunday in Atlanta ... and could be suspended as his team fights for their playoff lives.

As the game clock winded down in the fourth quarter at State Farm Arena, Murray and his teammates began leaving the court, but Dejounte made a detour, before heading for the locker room.

Check out the video ... Murray walks up to official Gediminas Petraitis, in his 8th season as an NBA ref, and appears to bump him with his chest. It's unclear if the contact was incidental.

Dejounte also appeared to say something to the ref, before starting to walk away. Seconds later, a visibly…