NASHVILLE (AP) — A Tennessee man was charged Wednesday in a scheme involving former Republican presidential nominee Mitt Romney's income tax returns during the 2012 campaign.

The U.S. Justice Department said a federal grand jury in Nashville indicted Michael Mancil Brown, 34, of Franklin, and charged him with six counts of wire fraud and six counts of extortion.

Brown is accused of having an anonymous letter delivered to the PricewaterhouseCoopers LLP accounting firm in Franklin last August, demanding that $1 million in digital currency be deposited to a Bitcoin account to keep some of Romney's income tax returns from being released. The Justice Department said Brown falsely claimed that he had gained access to the PricewaterhouseCoopers internal computer network and stolen tax documents for Romney and his wife, Ann Romney, for tax years before 2010.

A phone number listed for Brown had a message saying it was not receiving incoming calls. He did not immediately return an email message sent Wednesday evening.

The letter said interested parties who wanted the purportedly stolen returns released could contribute $1 million to another Bitcoin account. Bitcoin is a hard-to-trace form of electronic cash.

The Justice Department statement said similar letters were delivered to Democratic and Republican party offices in Franklin.

The letters claiming two decades' worth of the Romneys' tax returns had been stolen came amid last year's Republican and Democratic conventions.

At the time, Romney had steadfastly declined to release more than one year of tax returns, for 2010, and Democrats were trying to portray him as so wealthy he was out of touch with middle-class voters. Last fall, Romney also released his income tax returns for 2011.

Computer thumb drives were delivered with the demand. The letter said the tax returns delivered on the thumb drives were encrypted and more copies would be sent to "all major news media outlets" with the passwords to be released if payment wasn't made.