Coastguard and lifeboat teams person been tasked to a occurrence onboard a Stena Line ferry sailing from Cairnryan to Belfast.
A blaze broke retired successful the motor country of the Superfast VIII connected Monday astatine astir 21:00 BST.
Stena Line says the occurrence has present been extinguished.
The vas was owed to get successful Belfast astatine astir 21:45 section time. It is present being brought into Belfast with the assistance of the coastguard and tugs.
Lifeboats from Bangor, Donaghadee and Larne were tasked to woody with the incident.
Coastguard rescue teams from Bangor, Portaferry, Larne and Portmuck besides attended.
Passengers onboard had been advised to congregate successful designated areas aft an exigency was declared, erstwhile the ferry was successful Belfast Lough.
Speaking to BBC News NI, rider Chris Clotworthy said helium was travelling location to Northern Ireland from Glasgow, wherever helium had been for his daughter's graduation.
He said astatine astir 21:00 BST immoderate codification words were relayed implicit the intercom to the unit members onboard.
"Obviously, each sorts of things went done one's mind," helium said.
"The vessel did a implicit 180 grade crook and looked to beryllium heading backmost to Scotland, this was erstwhile it was level with Blackhead (in County Antrim). It past did different implicit 180 and stopped."
Mr Clotworthy said the ambiance onboard was "relatively calm".