US doughnut maker and retailer Krispy Kreme has said it hired an independent law firm to look into a matter related to an acquisition it made in the year to 1 February.

The company said in a filing to the Securities and Exchange Commission that the investigation discovered no "intentional misconduct" by Krispy Kreme or its employees in the matter, reported Reuters.

Krispy Kreme announced at the end of July that the US Securities and Exchange Commission is conducting an informal, non-public inquiry regarding the company.

Krispy Kreme said the inquiry concerns the company's franchise reacquisitions and its previously announced reduction in earnings guidance.

"Krispy Kreme has no higher priority than the confidence of our shareholders, customers and employees. While we are confident in our practices, we understand and respect the SEC's responsibilities and will continue to cooperate fully throughout this process," chairman, president and CEO Scott Livengood said when the inquiry was announced.