At one time 400 staff were employed at the plant
A food plant making Chinese ready meals in Swansea is set to be closed down, putting 234 jobs at risk.
Ethnic Cuisine's owners said it had decided to close the factory after failing to agree terms to supply products to major customer Sainsbury.
Northern Foods, which bought the firm in 2007, is starting a consultation "on a proposal to close the site," which it said was no longer profitable.
Sainsbury said the existing supply agreement "was no longer viable".
Around 60% of the workforce is Polish and translators had to be used to break the news.
The plant works 24 hours a day and with use of additional agency workers, the workforce rises to 400 during the winter, which is the season of peak demand for the food they make.
Managers said they had been trying to reach an agreement over the last couple of months but it could not be found.
Gary Walsh, MD of Northern Foods' microwave meals section, explained why the Swansea jobs were going
The deal with Sainsbury is worth 90% of the plant's business and there was a "very low probability" similar orders could now be found in time to save the factory.
A spokesman for Northern Foods told BBC Wales: "The site is not profitable today."
One worker, who did not want to be named, said they were told about the closure when they came in to start shift at 0800 BST and there had been no warning beforehand.
The jobs are mostly shift work in the food preparation and chilling area and the workforce includes a lot of agency staff.
The Swansea-based company, based on an industrial estate in Winch Wen, was founded in 1994 by Malaysian-born businessman Yow Meng Yap, with a workforce of 40.
Mr Yap, who was presented with an honorary OBE in 2007, grew the workforce to 400 within 10 years, making chilled Chinese ready meals for Sainsbury, its main customer.
Llansamlet councillor June Evans said the news came as a "shock"
"It's very disappointing. There are a lot of local people there - it's going to have an impact certainly."
Leeds-based Northern Foods also makes Goodfella's pizza and Fox's biscuits, as well as a wide range of ready meals, at sites in Carlisle, Grimsby and Sheffield, employing more than 2,000 people.
In a statement, Sainsbury's said: "Our priority is to meet our customers' needs for high quality, tasty, good value food, both now and in the future.
"Following extensive discussions with Northern Foods in Swansea we came to the conclusion that our existing supply agreement on ethnic ready meals was no longer viable for either party.
"This kind of decision is not one we take lightly and we worked closely with Northern Foods throughout the process."