The giant accounting firm PricewaterhouseCoopers says a claim by a hacker group that it stole Republican Presidential candidate Mitt Romney’s tax returns from an office in Tennessee does not appear to be true.

"We are aware of the allegations that have been made regarding improper access to our systems,” said Chris Atkins, the managing director of US public relations for the firm. “ We are working closely with the United States Secret Service, and at this time there is no evidence that our systems have been compromised or that there was any unauthorized access to the data in question."

The Romney campaign similarly told CNBC that it was aware of the claim. A Romney spokesman said “proper authorities” are investigating the allegation.

The claim appeared Wednesday on the website Pastebin.com, the same venue that had been used by Anonymous affiliated hackers to release what they said were one million unique identifying numbers of Apple computer products. (Read More: FBI Denies Hackers' Claim Of Apple ID Theft)