The Enterprise Minister said she could not give an assurance that there would not be further job losses at engineering firm FG Wilson, on 20 September 2012.
On 13 September 2012, the company announced 760 people were to lose their jobs across the its four Northern Ireland sites.
Appearing before Stormont's Enterprise Committee, Mrs Foster said Caterpillar, which owns FG Wilson, had given a commitment in writing that they saw a long-term future for their brand in Northern Ireland.
"I am confident that FG Wilson and the Caterpillar brand will remain in Northern Ireland. Am I confident that they won't make further redundancies? I cannot give that assurance," she said.
She said she was going to meet senior officials from the company in the United States to discuss how Northern Ireland was competitive in terms of higher-value work.
Mrs Foster also said she would be communicating "the devastation which they have visited upon families".
In response to concerns from committee members, the minister she was satisfied with the return FG Wilson had brought to the Northern Ireland economy.
The minister said Invest Northerthrn Ireland had put around £20m into the company. "over the period of time since Caterpillar came to Northern Ireland and they have invested £43m alone in research and development as a company".
The committee also agreed to invite the Health and Safety Executive (HSE) to appear before it following the death of four people in farming and industrial accidents in the same week.
Fermanagh GAA player Brian Og Maguire died in an industrial accident at a factory in the Ballyconnell Road area of Derrylin.
Two days later, Noel Spence and his two sons, Nevin and Graham, died after they were overcome by fumes from a slurry tank at their farm in Hillsborough, County Down.
Mrs Foster said the deaths had given her "a lot of cause for concern".
She added the HSE was investigating these "tragic events" and would bring forward a report.