After several days of speculation, ethanol producer VeraSun Energy Corp. and 24 of its subsidiaries have filed for Chapter 11 bankruptcy protection.

The Sioux Falls-based company said in a news release late Friday that the voluntary move was prompted by a reduction in liquidity and will allow it to continue operating normally.

VeraSun said higher corn costs, worsening capital markets and tighter trade credit were all factors.

The company is one of the nation's largest ethanol producers with 16 operations in South Dakota, North Dakota, Nebraska, Minnesota, Iowa, Michigan, Indiana and Ohio.

According the bankruptcy court filing in Delaware, VeraSun has more than $1.9 billion in debt and nearly $3.5 billion in assets.