CLEVELAND, Ohio -- Power plant company FirstEnergy Solutions Corp.and its subsidiaries, along with the FirstEnergy Nuclear Operating Co., filed for bankruptcy protection late Saturday night.

The filing in the U.S. Bankruptcy Court for the Northern District of Ohio indicates that the top unsecured creditor is the Bank of New York Mellon Trust Co. which is owed more than $1 billion. The company also owes the BNSF Railway Co. $72 million.

The company and its creditors, estimated at several hundreds in the filing, have been negotiating a settlement, the company said. Other documents including a summary of the company's assets and liabilities are due April 16.

FirstEnergy Solutions and its subsidiaries have over $550 million in cash, enough money to pay employees and suppliers and continue operations, the company said in a statement.

The FirstEnergy Corp., parent of FirstEnergy Solutions and the FirstEnergy Nuclear Operating Co., is not part of the filing.

In a separate statement, Charles Jones, CEO of FirstEnergy, said the company will focus on its regulated local and long distance transmission companies, which has been the goal of the company for at least 18 months. FirstEnergy is planning on investing up to $10 billion upgrading its delivery systems over the next three years.

The Easter Weekend Chapter 11 filing was made over the internet and is an effort to restructure at least $2.8 billion of debt FirstEnergy Solutions faces.

It follows years of efforts by the parent company to persuade Ohio regulators and lawmakers to approve multiple plans to wring more money out of customers to subsidize the power plant operations.

The bankruptcy filing caps a five-day media blitz that began with the announcement Wednesday evening that FirstEnergy Solutions had informed grid manager PJM Interconnection that it would close its three nuclear power plants within three years.

The company also informed the Nuclear Regulatory Commission of its shutdown decision on Wednesday, though only orally, which the NRC does not recognize as an official declaration.

On Thursday, the company filed a 44-page formal appeal to the U.S. Department of Energy to declare an emergency, under extraordinary power reserved for use during cataclysmic threats to the national electric grid such as war.

The company requested that Energy Secretary Rick Perry order PJM Interconnection, the manager of the high-voltage transmission grid in Ohio, 12 other states and the District of Columbia, to begin developing special provisions for owners of old nuclear and coal-fired power plants to help them survive PJM's competitive wholesale markets.

PJM responded Friday in a letter directly to Perry, saying there is no imminent threat to the stability of the grid, and that it would do another analysis of the grid's ability to remain stable despite the closing of old coal and nuclear power plants. PJM also noted that it would use federally approved analytical methods to complete the assessment in 30 days.

FirstEnergy has complained bitterly for several years that PJM has created competitive market rules that favor new, ultra-efficient gas turbine plants and wind turbine farms.

PJM's competitive market rules in fact favor the cheapest source of power needed at any given second to guarantee the stability of the thousands of miles of transmission lines under its control.

FirstEnergy wants PJM's market rules changed to reflect what it argues is the importance of its very large coal-fired and nuclear plants to the stability of the grid.

In other words, it wants PJM's competitive market to provide a way for its power plants to succeed against the newer, more efficient technologies offering power at lower prices.

That has galvanized consumer, business and environmental groups that see the company's problems as its own fault, beginning with its $4.7 billion purchase of Pennsylvania-based, coal-heavy Allegheny Energy in 2010. Though the the deal was a stock transaction, FirstEnergy also absorbed $3.8 billion of Allegheny's debt. FirstEnergy has since closed many of Allegheny's coal plants.

FirstEnergy is not the only utility to consider closing or to have already closed nuclear reactors. Five have closed since 2013. Another dozen nuclear plants were to have closed by 2022 or sooner, but new funding measures created in New York, Illinois and Michigan persuaded operators to remain open.

Saturday's late night bankruptcy petition prompted an immediate response from the Public Utilities Commission of Ohio.

Chairman Asim Haque issued a statement just after midnight pointing out that the the bankruptcy reorganization had been widely anticipated and that the development would not affect electric service.

"There is no reason for customers of FES - or anyone else in Ohio - to be concerned about whether or not they will have electricity. They will," he wrote.

Plain Dealer reporter John Caniglia contributed to this story