Humberside Police have sent a 'good luck' message to Albion fans for their crucial game on Sunday.
But the force has advised fans who don't have a ticket to stay away from Grimsby.
Brighton must win the Division One clash at Blundell Park to avoid relegation - and they'll still go down if Stoke win or draw against Reading.
All 2,500 away tickets for the game have been sold and no more will be made available.
Superintendent Sean White of the Humberside force said: "We wish Brighton success and we hope fans enjoy the game. This is an important day for the club and we recognise that.
"However, there are no more tickets available and anyone turning up on the day without a pre-purchased ticket will be turned away."
He said the match would be aired on Sky Sports and added: "There is an opportunity for supporters to watch the action live in their local pubs with friends and family and not make an unnecessary journey to Grimsby.
"There will be a strong and highly visible police presence in Grimsby and Cleethorpes throughout the whole of the Bank Holiday weekend.
"Public safety is our priority and for that reason we will be policing the match robustly in order to protect public safety."
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