Tribune Co. (TXA), the owner of several of the nation’s largest newspapers, said Monday it has filed for Chapter 11 bankruptcy protection. The company cited a $13 billion "heavy debt load" as the reason to seek protection.. 

The media giant, which owns The Chicago Tribune, The Los Angeles Times, the Orlando Sentinel and 23 television stations, was battered in the past year since its conversion to a private company under billionaire real estate investor Sam Zell.

According to the company, the Chicago Cubs franchise was not included in the Chapter 11 filing. The company will continue to look for ways to sell the franchise, including its historic Wrigley Field.

The entire newspaper industry is under pressure due to massive advertising revenue shortfalls and a general industry downturn as consumers have turned to the Internet. The troubles have accelerated as the U.S. has slipped into recession.

Earlier today, reports came out that the company hired investment banking firm Lazard Ltd. as its financial adviser and retained the law firm Sidley Austin to advise the company through bankruptcy. Tribune has used Sidley Austin for general business needs in the past.

Tribune has been cutting costs through newsroom layoffs, and raising cash through the sale of certain assets, including the Long Island, N.Y.-based Newsday and the ongoing sale of the Chicago Cubs baseball franchise. But its $13 billion debt load was too much for Zell and his company to handle in this difficult economic environment.

"Unfortunately, at the same time, factors beyond our control have created a perfect storm -- a precipitous decline in revenue and a tough economy coupled with a credit crisis that makes it extremely difficult to support our debt," Tribune CEO Sam Zell said in a statement.

Another complication stems from the frozen credit markets, which have made it difficult for prospective buyers to raise money to acquire Tribune’s assets. In addition, the difficult markets have made it nearly impossible for Tribune to refinance its debt.

According to the company, the filing will focus on restructuring its debt not its operations, so the closure or sale of newspapers may not be on the table as of yet.

Tribune, like its publicly-traded competitors The New York Times Co. (NYT), McClatchy (MNI), Gannett (GCI), have all seen rapid deterioration in their businesses since the recession began nearly a year ago. Advertising revenue is down double digits, while newsprint and debt costs have escalated. Moody’s rated The New York Times’ debt as “junk” earlier this month on business concerns.