WASHINGTON, Dec 20 (Reuters) - The United States filed a civil forfeiture complaint on Monday to return more than $154 million in funds that were allegedly stolen from a subsidiary of Tokyo-based Sony Corp (6758.T) and then seized by law enforcement during the FBI’s investigation of the theft, the U.S. Justice Department said. Rei Ishii, an employee of Sony Life Insurance Company Ltd in Tokyo, allegedly embezzled the property in May and converted it to more than 3,879 Bitcoins valued today at more than $180 million, the department said in a statement. Those funds were seized by law enforcement on Dec. 1, based on the FBI investigation, it said. Ishii allegedly falsified transaction instructions, causing the funds to be transferred to an account he controlled at a bank in La Jolla, California, and converted them to Bitcoin, according to the complaint filed in federal court in the Southern District of California. "All the Bitcoins traceable to the theft have been recovered and fully preserved. Ishii has been criminally charged in Japan," the Justice Department said.