SolarWorld has confirmed it has tightened its IT security after being informed that the Chinese military allegedly stole thousands of documents from its computers in 2012.

An FBI investigation claims to have uncovered the breach. It was followed up on Monday with the indictment of five military officer in the Chinese People’s Liberation Army by a Grand Jury in Pennsylvania.

“Immediately after the intrusions came to light, SolarWorld further tightened its IT security,” the company said in a statement. “We are deeply troubled by these allegations that Chinese military officials illegally hacked into our computer systems.”

The company said that the charges reinforce its own controversial claims that Chinese solar manufacturers were willing to go to great lengths to damage the US solar industry.

“It’s yet another example of the Chinese government’s systematic campaign to seek unfair advantage in the US and global solar industry. Already, dozens of US companies have closed operations, and thousands of US employees have lost their jobs,” SolarWorld said.

The Chinese Ministry of Defence has denied the claims and called on the US to explain its own cyber security breaches.

State news service Xinhua quoted Ministry spokesperson Geng Yansheng as saying that the charges seriously damaged the trust between the two nations and the chances of a healthy, steady and reliable military relationship forming.