Shanshan Du and Yu Qin, both of Troy, were indicted on conspiracy, fraud and other charges. They had been under scrutiny for years and were charged in 2006 with destroying documents sought by investigators, a case that was dropped while a broader probe was pursued.
The indictment says Du, who was hired at GM in 2000, purposely sought a transfer in 2003 to get access to hybrid technology and began copying documents by the end of that year.
In 2005, she copied thousands of documents, five days after getting a severance offer from the automaker, according to the indictment.
By that summer, Qin was telling people he had a deal to provide hybrid technology to Chery Automobile, a GM competitor in China, the indictment says. The couple had set up their own company, Millennium Technology International.
Outside court, Assistant U.S. Attorney Cathleen Corken said there's no indication the Chinese benefited.
Jin Yibo, a Chery spokesman in China, said early Friday that the company saw a news report about the case but knew nothing else about it.
"We are surprised about why anyone connected this with Chery. This is ridiculous," Jin said.
Du, 51, and Qin, 49, were arrested Thursday and remained mostly silent during a court appearance where they waived a reading of the indictment. Not-guilty pleas were entered for them. The maximum penalty if convicted is 20 years in prison.
"Theft of trade secrets is a threat to national security," Andrew Arena, head of the FBI in Detroit, said in a statement.
Du's attorney, Robert Morgan, declined to comment. Qin's attorney, Frank Eaman, said he was "completely surprised" by the indictment.
"This investigation has been going on so long I figured if they had a basis they would have charged them a long time ago," Eaman said.
Corken said GM learned about the alleged theft and called the FBI. GM estimates the value of the stolen information at $40 million.
In May 2006, Du and Qin were charged with destroying records to stifle an investigation of them. FBI agents followed them to a major grocery store where Qin approached a Dumpster, according to a court filing at the time. Agents later retrieved shredded documents.
That criminal complaint was dropped less than two months later, a common move when investigators want to further develop a case. The indictment includes an obstruction of justice charge against Qin for the alleged Dumpster incident.
Du and Qin, both U.S. citizens, were released on bond and ordered to mostly stay in the Detroit area.