The FBI has arrested a contract employee at General Motors Corp.'s Photographic Labs in Detroit, charging him with stealing confidential sketches and pictures of future car models that GM says cost it hundreds of millions of dollars in trade secret damage.

Arrested was Gregory C. Hooper, 36, of Royal Oak, Mich. The FBI maintains that Hooper, who worked for two years at GM on a contractual basis, stole and sold numerous pictures of future GM models to several automotive publications and also attempted to sell those pictures back to the giant carmaker for $75,000.Hooper is charged with mail fraud in relation to obtaining money from GM, U.S. Attorney Stephen J. Markman said.

Other charges are possible pending further investigation.

Markman and other FBI officials said the industrial espionage case, which was started in June, represents "one of the largest losses of this kind" and that it has "cost hundreds of millions of dollars in lost confidential trade secrets for General Motors.

"It is not the quantity of the documents . . . it is the value to the firm that lost those documents," Markman said, while another FBI official said Hooper appeared to have "strictly a profit motive."

GM said that "such a crime has a profound impact" on its future competitive position, and that it will continue to cooperate with the FBI in its investigation.

The case stems from late last year, when several auto enthusiast magazines, including Automobile Magazine, published confidential design studio photographs of GM's new Saturn car, as well as some other GM models not slated to debut until the 1993- or 1994-model years.

GM immediately began offering $30,000 rewards for information leading to the apprehension of any employee who steals confidential documents, photos and drawings. But GM spokesman Don Postma said the automaker has never paid out on the program.

Markman said it is not yet clear if those publications are culpable, since it has yet to be determined if they knowingly purchased stolen goods.

The FBI is also still probing to see if Hooper attempted to sell the confidential GM pictures to other automakers, he said.

Hooper, released by the FBI on a $10,000 unsecured bond, could face up to five years imprisonment and a $250,000 fine if convicted.