Megaupload users may never be able to re-access their files following the U.S. government's announcement late Monday that digital storage firms contracted by the shuttered company will begin deleting files Thursday this week.

Federal prosecutors have earlier indicated that Megaupload servers located in Virginia have been seized on the strength of search warrants but their contents cannot be accessed.

According to the Associated Press, the U.S. Attorney's Office for the Eastern District of Virginia identified on Friday the storage companies as Carpathia Hosting Inc. and Cogent Communications Group Inc.

Any attempts by Megaupload users to recover their personal files must be course through these two firms, the prosecutors said.

However, a statement issued by Carpathia on Monday denied that it can access the personal files of millions of users trapped in the Megaupload servers when the U.S. government cracked down on its operations earlier this month.

"It does not have, and has never had, access to the content on Megaupload servers," Carpathia was quoted by AP as saying in a statement.

Customers' concern over the fate of their files must be settled with Megaupload officials, the company added.

But Megaupload legal representative, Ira Rothken said on Sunday that the company is virtually unable to do anything following the arrest and detention of its key officials.

The U.S. government has ordered a freeze on Megaupload funds, Rothken said, but he assured that he has been coordinating with federal prosecutors to prevent the two storage firms from deleting the files of up to 50 million users.

The Megaupload lawyer added that aside from protecting the personal files of its users, the company also need to access some files on the seized servers, which will be used to defend the company.

"We're cautiously optimistic at this point that because the United States, as well as Megaupload, should have a common desire to protect consumers, that this type of agreement will get done," Rothken told AP.

The U.S. government has clamped down on Megaupload's operations, accusing the firm of online piracy by distributing illegal copies of music, movies and softwares that led legitimate companies to lose hundreds of millions.

Its founder and CEO, Kim Dotcom, was arrested in New Zealand, holed up in his multi-million mansion, and is under detention without bail.