Chelsea are investigating claims a steward injured during the Manchester United game was hit by an object thrown from the crowd.
The official was taken to hospital with a twisted knee suffered when he fell in the aftermath of Javier Hernandez's winner.
The United striker's celebration brought an angry response from the home supporters, and a Chelsea spokesman confirmed the possibility something was thrown from the Matthew Harding Stand.
He said: "We are looking at reports of objects that may have been thrown or incidents around the steward taking a fall. We are investigating all the incidents around that time.
"My information so far is that he slipped and fell, may have hurt his knee, and was being treated by the side of the pitch. He's been taken to hospital."