WASHINGTON (Reuters) - Rubycon Corp, Elna Co Ltd 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.

Rubycon and Elna, both from Japan, and Holy Stone, which is based in Taipei, will each plead guilty to a single count of price-fixing, which is a felony, the department said in a statement.

Electrolytic capacitors regulate current in electronics such as airbag systems, computers, televisions and a host of other devices.

Two other companies, NEC TOKIN and Hitachi Chemical Co Ltd, previously pleaded guilty to conspiring to fix prices of capacitors, also known as condensers.

Rubycon and Elna did not immediately respond to a request for comment while Holy Stone declined to comment.

(Reporting by Diane Bartz; Editing by Alan Crosby)