After a setback, federal prosecutors are fighting to salvage their aggressive economic espionage case against four Chinese corporations accused of paying close to $30 million for stolen DuPont trade secrets.

But U.S. District Judge Jeffrey White still seems skeptical the government has lawfully served the Chinese entities under the rules of federal criminal procedure. Prior to hearing Thursday, White issued a tentative ruling quashing service of indictment against two of the four companies. He did not rule from the bench or indicate his views as to the other two entities.