The general manager of the Professional Game Match Officials Board told Sky Sports News: "You would like to think the match officials, the three of them, would have spotted the ball had crossed the line.
"You would first of hope they have spotted that particular incident. Under law, the fourth official is not allowed to assist in the process had he seen it.
"It is disappointing. I have spoken to Neil Warnock this morning and apologised to him on behalf of the match officials and, of course, the PGMOB, and I make a public apology to the players and also the spectators of Palace.
"They travel away, they spend a lot of money and it is very disappointing that when the ball does strike the net, it is ruled out and not given."