A U.S. grand jury has charged five Chinese men with economic espionage and trade secret theft. (AP Photo)

A federal grand jury in Pittsburgh has found that five Chinese People's Liberation Army members hacked into the computers of a number of businesses and organizations in western Pennsylvania -- including U.S. Steel, Westinghouse Electric, and United Steel Workers.

According to an indictment unsealed Monday, the Chinese men -- Wang Dong, Sun Kailiang, Wen Xinyu, Huang Zhenyu and Gu Chunhui --  have been collectively charged with 31 crimes. This is the first criminal indictment against state-sponsored hackers who allegedly engaged in cyberespionage for economic purposes, according to the Justice Department. And the FBI said it's just the beginning of a larger crackdown.

The government said the accused were members of  PLA Unit 61398, a military group based in Shanghai. Last year in a widely reported investigation, the cybersecurity firm Mandiant identified this group as a source of economic cyberspying.

At a press conference Monday morning, government officials alleged the defendants hacked into the computer networks of companies as they engaged in trade disputes or competed against Chinese companies for major contracts -- stealing both technical trade secrets and strategic information. In some cases, the U.S. government alleges, the stolen information was used to benefit Chinese state-sponsored companies.

David Hickton, the U.S. attorney for the Western District of Pennsylvania,  said there had  "a real and demonstrable loss of jobs" as a result of ongoing Chinese cyberespionage. He did not provide a dollar amount on the damage related to the cases announced Monday.

Bob Anderson, the executive assistant director of the Criminal, Cyber, Response and Services Branch at FBI headquarters, said this first indictment "cleared the way" for additional charges in the future. "This is the new normal," Anderson said, adding that the public could expect to see new charges on a regular basis, "not just every six months" or every year.

Anderson said the investigation had been ongoing for several years, involved 46 field offices and should serve as a "wake-up call" to foreign governments that the United States will pursue the perpetrators of such crimes.

In his 2013 State of the Union address, President Obama cited cyberespionage as a major economic security issues. "We know foreign countries and companies swipe our corporate secrets," he said. "We cannot look back years from now and wonder why we did nothing in the face of real threats to our security and our economy."