WASHINGTON (Reuters) - Rubycon Corp, Elna Co Ltd <6972.T> and Holy Stone Holdings Co, Ltd have agreed to plead guilty to fixing the prices of electrolytic capacitors sold in the United States, the Justice Department said on Monday.

The plea agreement is the latest in a long-running international probe into price fixing of auto parts. Each of the companies faces a single count of price-fixing, which is a felony.

(Reporting by Diane Bartz; Editing by Alan Crosby)