Police are understood to be investigating reports of a missile being thrown during Coventry City's 3-1 defeat at Tranmere Rovers.
An object which looked silver in colour, was thrown down the left hand side of the away end at Prenton Park in the direction of an assistant referee who had failed to give Cyrus Christie a corner in the 62nd minute.
The incident was spotted by two stewards at the front of the stand who immediately radioed through the act of something being thrown.
Anyone caught throwing missiles can expect a fine and a three year ban from matches if found guilty.