Two family members were charged Wednesday in a federal case against a Chinese-American engineer accused of trying to send sensitive information about Navy warships to China.

An indictment returned by a grand jury in Santa Ana charged Yui "Billy" Mak, 26, and his mother, Fuk Heung Li, 48, with making false statements and acting as agents of a foreign government, namely China, without prior notification to the U.S. attorney general, said FBI spokeswoman Laura Eimiller.

Yui Mak is the nephew of Chi Mak, who is accused of taking computer disks from an Anaheim defense contractor where he was lead engineer on a sensitive research project involving propulsion systems for Navy warships. Li is married to Chi Mak's brother, Tai Wang Mak, also a defendant.

Yui "Billy" Mak was arrested Wednesday in Alhambra, east of Los Angeles, and was scheduled to be arraigned Thursday. Li, previously indicted on federal marriage fraud charges, is free on bond and is expected to be arraigned in the current case in July.

Wednesday's superseding indictment retained the original charges against Chi Mak, 65, his wife, Rebecca Laiwah Chiu, 62, and Tai Wang Mak, 56. Each faces a count of failing to register as a foreign agent.

"We continue to maintain our clients' innocence," said Chi Mak's attorney, Ronald Kaye. "The government has overstated the evidence and misconstrued what was stated by my client."

Failing to register as a foreign agent carries a maximum 10-year prison sentence, while false statements carries a maximum of five years.

The government claims that Chi Mak, who is a U.S. citizen, allegedly passed the information to his brother, who then encrypted or helped encrypt the files and loaded them onto a computer disk.

Prosecutors have said previously that authorities recovered from the disk restricted documents on the DDX Destroyer, an advanced technology warship. They also allege that they found two lists in Chinese asking Mak to get documents about submarine torpedo technology, electromagnetic artillery systems, weapon standardization, early warning technology used to detect incoming missiles, and defenses used against nuclear attack.

The FBI arrested Chi Mak and his wife in October for investigation of conspiracy to steal U.S. government documents. They have not been charged with that allegation.

John Early, attorney for Tai Mak, pointed out his client had not been charged with espionage despite the allegations in the case.

The Chinese Foreign Ministry had no immediate comment about the case.