The U.S. has charged five Chinese military officers for hacking into American nuclear, metal and solar companies to steal trade secrets.
Companies that the suspects targeted include Alcoa (AA), Allegheny Technologies (ATI), United States Steel (X), Toshiba (TOSBF) unit Westinghouse Electric, the U.S. operations of SolarWorld (SRWRD), and a steel workers' union.
Officials said the firms suffered "significant" losses, although they declined to provide details.
Alcoa said that to its knowledge, "no material information was compromised."
The U.S. probably won't be able to prosecute the officers, as China is unlikely to hand them over.
The charges come amid long-running tension between the U.S. and China over cyber-espionage. Documents leaked by Edward Snowden show that the U.S. has tampered with Cisco-made equipment that was for sales overseas.