Greencore expects to take a €9m (£7.1m) hit to its operating profits in 2008 following the revelation that a former executive concealed costs in its mineral water business.
The scandal is a fresh blow to the Irish group, already bracing itself for a fall in full-year profits due to soaring ingredients costs and the weakness of the pound against the euro.
The ongoing investigation could also lead to a further restatement in _profit of €8m in 2007 and €4m in 2006.
Greencore said it believes the cover-up was undertaken by the former financial controller of the Mineral Water business, who left the business prior to the fraudulent activity being uncovered. Three senior managers with direct supervisory responsibility for the former financial controller have also left the company.
The potential fraud first came to light on 6 June after a review by the internal audit function uncovered irregularities in the business' accounts.
Greencore Mineral Water is the UK's largest provider of own-label water, supplying some 200 million litres to retailers including Asda and Waitrose. It has an annual turnover of €40m.
A spokesman said a new management team was at the water business and the company did not anticipate an adverse effect on sales.