Nine crew members have been injured after a fire on board a Canadian submarine sparked a major rescue operation off the west of Ireland.
HMS Upholder was sold to the Canadians
The HMCS Chicoutimi is now drifting without power in poor weather.
The Ministry of Defence said there were no plans to remove any of the 50-strong crew from the vessel.
The accident happened as the submarine was making its way to Canada after being officially handed over to its new owners by the Royal Navy on Saturday.
Irish Minister for Defence Willie O'Dea said the LE Roisin, which was on routine patrol off the north west coast, was travelling to the area and should arrive around midnight BST.
A Canadian Forces spokeswoman confirmed that the crew was safe.
Captain Holy Apostoliuk said: "The submarine,
while transiting from UK to Canada, experienced a fire while at sea off the west coast of Ireland.
"The submarine and its Canadian crew left Faslane on 4 October and was en route to Halifax, Nova Scotia, when the fire occurred.
Type: Long-range diesel-electric patrol submarine
Displacement: 2,185 tons (surf.), 2,400 tons (sub.)
Length: 70.26 metres
Speed: 12 kts (surf.), 20 kts (sub.)
Patrol Endurance: approx 8 weeks
Complement: 48 crew, 5 trainees
Diving Depth: 200 metres
"The cause of the fire has not been determined but it was contained and is now out."
She said that the sailors who experienced smoke inhalation did not need to be evacuated from the vessel.
"The submarine is currently without propulsion north west of Ireland," she added.
A Royal Air Force Nimrod from Kinloss was diverted to the area and a Royal Navy Sea King helicopter was sent from HMS Gannet in Ayrshire.
"The Canadian Forces are working in co-operation with the Royal Navy, who will assist the Chicoutimi as required," the Canadian spokeswoman said.
"We are in the process of informing family members."
The alarm was raised by the captain of the submarine, which is not nuclear-powered or carrying nuclear warheads, shortly after 1500 BST on Tuesday.
The request for assistance came from the vessel some 100 miles north west of Ireland.
Neil Smith, a spokesman for the Faslane submarine base on the Clyde, said that the Royal Fleet Auxiliary vessel Wave Knight had turned round and was on its way to the scene.
A Type 23 frigate, HMS Montrose, was being sent from Faslane, accompanied by tug boat support.
A Faslane spokeswoman said that the electrical fire on board the Chicoutimi had resulted in smoke throughout the vessel.
"She is now on the surface and everything appears to be all right," she said.
The MoD confirmed that nine people had been injured on board the submarine.
Weather conditions in the area have been described as extremely bad, with rough seas.
The Chicoutimi was originally built for the Royal Navy, when it was known as HMS Upholder.
It was bought by the Canadian Navy, where it is now one of four Victoria Class long-range patrol submarines.
Canadian MP Bill Casey said there had been a series of problems with the vessels.
"They have experienced overheating, they have experienced leaks, they have experienced rust," he said.
"They have had to have the exhaust valves replaced, which is a huge valve in the middle of the boat which redirects the exhaust whether the boat is submerged, partially-submerged or on the surface.
"They have been plagued by a lot of problems."
The Chicoutimi was renamed and formally handed over to its new owners during a ceremony at Faslane on Saturday.
The vessel had been due to arrive in Halifax, on the east coast of Canada, on 18 October.
This is the second time in a month that the Chicoutimi has been involved in a rescue at sea.
Last month, she was involved in an incident when an ocean-going tug boat accompanying it ran aground off Skye during sea trials.
Eight sailors were taken off the tug by Portree lifeboat.