WASHINGTON — The Secret Service says it’s investigating the reported theft of copies of Republican presidential candidate Mitt Romney’s federal tax records before 2010. A letter sent anonymously to Tennessee political and newspaper offices demanded $1 million to prevent their disclosure.

Romney’s accounting firm, PricewaterhouseCoopers, said there is no evidence any Romney tax files were stolen. The letter said the returns were stolen in late August during a Watergate-style break-in at the company’s accounting offices in Franklin, Tenn.

A Tennessee Republican official, Jean Barwick, confirmed she received the letter and an encrypted flash drive, and said she turned them over to the Secret Service. She was not able to confirm that copies of any tax returns were stored on the flash drive.

Secret Service spokesman Edwin Donovan confirmed the agency is investigating.

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