Niwot, Colo. -- The auditor of Crocs Inc. says it has "substantial doubt" about the ability of the shoemaker to stay in business amid falling revenue.

Crocs, maker of the colorful plastic shoes, disclosed the opinion of Deloitte & Touche LLP in an annual report filed Tuesday with the Securities and Exchange Commission.

The company said it is in discussion to replace its current revolving credit facility, which matures on April 2, but if it cannot secure additional financing and continues to lose money, "we may be unable to maintain a level of liquidity necessary to continue operating our business," Crocs said in the filing.

Crocs officials didn't immediately return a phone message Wednesday.

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