The US telecommunications company Tellabs, is to close its plant in Drogheda, Co Louth, by the end of the year, with 200 job losses.
70 workers are to be let go immediately and the remaining 130 jobs will be phased out over the next four months. The plant will close in December.
The workers were told of the closure this lunchtime.
The Tellabs plant opened in Drogheda just three years ago. The company also employs 600 people in Shannon. It is not yet clear if the jobs there are under threat.
It is understood the Tanaiste Mary Harney was informed of the company's plan to close the Drogheda plant last night.