Construction company Dawnus – which employs 700 people – has gone into administration, it has been confirmed.
Administrators Grant Thornton said the Swansea-based firm had gone bust on Friday after work was halted on several UK projects.
Contractors were called to a meeting on Thursday where they were told Dawnus had been placed into administration.
Administrator Alistair Wardell said the group faced a “wide variety of challenges”.
He added: “Whilst the financial difficulties of the group were not a consequence of Brexit, there is no doubt that Brexit uncertainty impacted the ability to rescue the business.”
The group is currently working on 44 construction sites across the UK and work on Swansea’s £12m Kingsway redevelopment was stopped on Wednesday amid the uncertainty.
Three school projects in Powys and a road in Fishguard, Pembrokeshire, are among those affected.
Three school projects in Powys and a road in Fishguard, Pembrokeshire, have also been affected.
Adrian Waters, of Pontypool-based construction company AP Waters, said he decided not to accept contracts from Dawnus after delays in payment for a project in Rhondda Cynon Taff.
“We work on tight margins and when there are delays in being paid it has a massive impact,” he said.
His company, which has 100 employees, was contracted by Dawnus to work on a project at a recycling centre in Hirwaun three years ago, he said.
“We did get paid in the end – but there were a couple of things we weren’t comfortable with and we decided not to take any more contracts with them.”
Reacting to the news Dawnus was in administration, Mr Waters said he felt sorry for everyone involved in the supply chain.
“So many businesses are going to take the brunt of this. Small businesses. Family businesses.
“I dread to think how much money they owe in total – and when this happens, you may only get a couple of pence in the pound back.”
What is Dawnus?
Dawnus has its headquarters in Swansea but runs construction projects across the UK and overseas.
The most recent company accounts show the company had a turnover of £170m in 2017, but posted a pre-tax loss of £1.35m.
Last September, the company said it employed 700 people.
As well as domestic construction, it previously operated in west Africa and worked on projects during the Ebola crisis.
In August, during a UK trade mission to South Africa attended by Prime Minister Theresa May, Dawnus was unveiled as part of a consortium targeting overseas aid contracts.
The company told BBC Wales in September it felt optimistic about life after Brexit because of the opportunities for overseas work.
Grant Thornton is not taking over any international operations at Dawnus International, Dawnus Sierra Leone or Dawnus Liberia.