Administrators have been officially appointed to the Harland and Wolff shipyard in Belfast.
In a statement, BDO Northern Ireland said after a long process in which a buyer could not be found, the business has been unable to continue trading.
It said this was down to having insufficient funds following the recent insolvency of its parent.
The move could put 125 jobs at risk.
"The team at BDO have engaged immediately with Harland and Wolff employees and other stakeholders to take all necessary steps to ensure they are supported throughout the administration process."
GMB regional organiser Michael Mulholland said trade unions remain in talks with the administrators about retaining a number of staff to maintain the site.
Harland and Wolff workers voted on Monday to continue their round-the-clock occupation of the site.
Unite regional organiser Susan Fitzgerald warned then that no administrator would be able to drive on to the shipyard site without the permission of the workers.
"No-one moves on to that site or off that site unless the workforce, who are running that site, agree to it," she said.
Harland and Wolff, one of Northern Ireland's most historic brands, is facing closure after its trouble-hit Norwegian parent company Dolphin Drilling failed to find a buyer.
Workers have occupied the site since last Monday as part of a high-profile campaign to save the yard.
They have called on the Government to step in to rescue the operation, potentially through nationalisation, but the Government has declined to intervene, insisting it is a commercial issue.
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Officials insist that EU state aid rules limit the scope to offer financial support through public funds.
On Monday evening a Government spokesman said Secretary of State Julian Smith "has made it clear that he will continue to do everything he can to secure the future of this historic site and ensure workers' interests are protected during this difficult time".
Workers are due to take part in a conference call with Mr Smith later.
The shipbuilder, whose famous yellow cranes Samson and Goliath dominate the Belfast skyline, employed more than 30,000 people during Belfast's industrial heyday, but now the workforce only numbers around 125.
It has diversified away from shipbuilding in the past two decades and until recently had primarily worked on wind energy and marine engineering projects.
Famed for building the doomed White Star liner Titanic, which sank on its maiden transatlantic voyage in 1912 after striking an iceberg, Harland and Wolff was one of the UK's key industrial producers during the Second World War, supplying almost 150 warships.