Cleveland-Cliffs Inc., which makes iron ore pellets used to produce steel, said Friday it will delay filing its annual report due to a probe into the company's revenue recognition practices.

The delay results from an internal probe into a specific contract revenue accounting item in the fourth quarter. The probe was triggered by an anonymous call into the company's ethics hot line. On Wednesday, Cleveland-Cliffs' audit committee determined the allegation was unfounded.

However, an outside audit by Deloitte & Touche continues and prevented the company from filing its annual report on Thursday. The review concerns cash payments for sales out of the company's ore stockpiles under a customer contract, but – at the customer's request – the ore was not delivered, Cleveland-Cliffs said in a statement.

As a result, Cleveland-Cliffs said its fourth quarter results may be subject to revision.

In late February, the company reported earnings of $1.59 per share on revenue of $622.6 million.

Shares of Cleveland-Cliffs slipped 30 cents to $56.44 in morning trading on the New York Stock Exchange.