A judge in California has ordered two Chinese nationals held without bail on charges of stealing U.S. warship technology. Authorities say the suspects are part of a scheme involving two brothers and their wives, and all four face criminal charges.

Prosecutors say Tai Wang Mak, a broadcast and engineering director for the Phoenix North American television channel, and his wife, Fuk Heung Li, were carrying encrypted disks with information on U.S. submarine technology when they were arrested. They were taken into custody October 28 at Los Angeles International Airport, en route to Guangzhou, China.

The two were charged with theft of government property, conspiracy, and transporting stolen goods. Mr. Mak's brother, Chi Mak, and his wife, Rebecca Laiwah Chiu, face similar charges. Chi Mak, an electrical engineer for the U.S. defense contractor Power Paragon, appeared in court last week and was also denied bail. Bond for his wife was at 300-thousand dollars. She will be subject to house arrest with electronic monitoring pending the outcome of the case.

Authorities say Chi Mak headed a research project on quiet propulsion systems for warships, and that he e-mailed documents and photographs from work to his home computer. He allegedly copied sensitive information onto CDs with the help of his wife, then passed the information to his brother who, prosecutors say, encrypted it.

Chi Mak is a naturalized U.S. citizen and his wife is American of Chinese descent. Tai Wang Mak and his wife are Chinese nationals who have been U.S. residents since 2001. U.S. authorities describe them as foreign intelligence officers, and say Chi Mak has been sending sensitive information to China since the 1980s, on topics that include the Aegis weapon system used on U.S. warships.

None of the four will face charges of spying, however.

At Monday's hearing, Tai Wang Mak's defense attorney said no one has shown that the information on the disks was classified.

Investigators have seized documents and computer data from Chi Mak's home in the Los Angeles community of Downey, and officials say the investigation is ongoing.