The person spoke to The Associated Press on condition of anonymity Monday because the Dolphins hadn't commented on the test results.
Pouncey left Sunday's game against the New York Giants in the second half with a neck injury after taking a blow to the head. He said that he briefly couldn't feel his legs, but that he felt fine after the game.
With Pouncey out, the Dolphins gave up four sacks in the fourth quarter, blew a late lead and lost to fall to 0-7. They play Sunday at Kansas City.