Brentford have contacted the police after a rugby ball was sent towards the pitch during their match against Liverpool.
Footage of the incident has circulated on social media. The ball was kicked from the roof of a high-rise building near the stadium and appeared to land on the roof of the east stand before bouncing on to the pitch.
A stadium employee later removed the ball from the playing surface.
The match ended in a 2-1 defeat for the hosts.
