A Chinese-American engineer and two family members who allegedly conspired to steal sensitive information about Navy warships and smuggle it to China were indicted Tuesday on federal charges, authorities said.

The grand jury indictment charges Chi Mak, 65, his wife and brother with acting as agents of a foreign government without prior notification to the U.S. attorney general, according to the U.S. attorney's office.

Federal officials said Mak took computer disks from Anaheim defense contractor Power Paragon, where he was lead engineer on a sensitive research project involving propulsion systems for Navy warships.

He and his wife, Rebecca Laiwah Chiu, 62, then copied the information to CDs and delivered them to Tai Wang Mak, 56, who was scheduled to fly to Hong Kong on Oct. 28 with his wife, Fuk Heung Li, an FBI affidavit said.

From there, the brother allegedly planned to travel to Guangzhou, China, to meet a contact.

Ronald Kaye, Chi Mak's attorney, said he had not yet seen the indictment, but noted his client was presumed innocent. His brother's attorney, John Early, had no immediate comment.

Chiu's attorney, Stanley Greenberg, said she was a loyal American citizen and suggested the charges might be trumped up.

"In recent years the government has brought similar charges but when called to proof, those cases resulted in little or nothing," Greenberg said. "I believe this case will follow that same pattern."

All four suspects were arrested on Oct. 28. Though Li was accused in an FBI affidavit of aiding the others, she was not indicted Tuesday.

Chi Mak and his wife are naturalized U.S. citizens originally from China. Mak's brother is a Chinese national and director for the Phoenix North American Chinese Channel. The brother's wife also is a Chinese national.

The two brothers were being held without bond, while Chiu was released after posting $300,000 bond.

"This was an appropriate charge given that the defendants were acting in the United States at the direction of the PRC [People's Republic of China]," Assistant U.S. Attorney Deirdre Eliot said.

Although it is not alleged in the indictment, authorities have said they recovered restricted documents on the DDX Destroyer — known as the "destroyer of the future" — that had been produced by the Naval Surface Warfare Center.

Also seized were documents on how to reconfigure a damaged ship after an attack, as well as two lists in Chinese that asked Chi Mak to get documents dealing with submarine torpedoes, electromagnetic artillery, early warning technology to detect incoming missiles and defenses against nuclear attack, prosecutors said.

The case comes as China — mindful of U.S. support for Taiwan — is seeking to strengthen its naval capabilities so it can function in the open sea as opposed to hugging shallow coastal waters, prosecutors have said.