The auditors to Riverdeep, the publishing company associated with businessman Barry O'Callaghan, have drawn attention to the firm's large debt burden.
Riverdeep, which has an office in Dublin, is part of Houghton Mifflin Harcourt and specialises in educational publishing and interactive learning technologies.
Auditors Pricewaterhouse Coopers (PWC) said there was a "material uncertainty'' which could cast significant doubt over the company's ability to repay or refinance its debt.
PWC added: "The financial statements do not include any adjustments that would be necessary if the company were unable to continue as a going concern''. The statement was signed off on January 26.
The precise debt on the balance sheet is not known as it remains an unlimited company with no requirement to publish financial statements.
Almost a year ago, Education Media & Publishing Group, the holding company that owns Houghton Mifflin Harcourt, restructured about $4bn (€2.95bn) of the publisher's $7bn debt load by converting it to equity, wiping out many of the original equity investors, including Mr O'Callaghan.
At the time Mr O'Callaghan said his priority was to fix the corporate balance sheet. However, a key market for the company, US educational pub- lishing, has been struggling amid steep cutbacks in state and municipal budgets.
Riverdeep was the original company Mr O'Callaghan was associated with, but it merged with Houghton Mifflin in 2006.