Nic Naitanui allegedly racially abused on pitch

West Coast ruckman Nic Naitanui was allegedly the subject of racial abuse in Sunday's western derby loss to Fremantle.

Domain Stadium - where the game was played - is investigating the incident.

A crowd member allegedly shouted out the abuse from the eastern end of the stadium.

"It's disappointing someone's crossed the line. I'm sure there's going to be a full investigation about it," Eagles midfielder Andrew Gaff said.