Japan’s No. 1 weapons manufacturer Mitsubishi Heavy Industries (MHI) has launched an investigation into a cyberattack that reportedly targeted data on its missiles, warships and nuclear power facilities.

The company confirmed that viruses were discovered on more 38 computer terminals and 45 servers in mid-August -- and informed police about the attack at the end of the month.

While the Japanese government said as far as it knows no sensitive information was released, the defense ministry was reportedly angered by the company’s security breach and pushed for an immediate probe into its cause. Tokyo officials were also outraged by MHI’s delay in informing the government about the cyberattack; reportedly, the defense ministry was not notified until Monday.

Defense minister Yasuo Ichikawa, speaking at a press conference on Tuesday, demanded that MHI undertake a review of their information control systems.

Ichikawa added: The ministry will continue to monitor the problem and conduct investigations if necessary.”

Reuters reported that a defense ministry spokesman said; It's up to the defense ministry to decide whether or not the [leaked] information is important. That is not for Mitsubishi Heavy to decide. A report should have been made.

These are believed to be the first cyberattacks against the Japanese defense ministry and apparently originated outside MHI’s computer network, the company said.

Japanese television broadcaster NHK noted that the viruses targeted a shipyard in Nagasaki, where MHI builds destroyers; as well as a facility in Kobe that makes submarines and parts for nuclear power stations; and a plant in Nagoya, where the company builds guidance and propulsion systems for rockets and missiles.

In the event the sensitive security information was indeed leaked, the defense ministry will likely penalize MHI, according to reports. Such punishment might include monetary fines or the cancellation of government contracts.

Another Japanese defense contractor, IHI Corp, which provides engine parts for military aircraft, also said it was targeted by cyberattacks, although its internal security systems prevented infection.

Neither MHI nor the government has speculated on who might be behind the attacks, although a Japanese newspaper reported that a Chinese language script was detected in the attack against the company.

This charge elicited indignation in Beijing.

China is one of the main victims of hacking. ... Criticizing China as being the source of hacking attacks not only is baseless, it is also not beneficial for promoting international co-operation for internet security, said Chinese foreign ministry spokesman Hong Lei.

However, China has long been accused of conducting cyberattacks on foreign governments and agencies. BBC reported that the U.S. military is increasingly worried about China’s alleged hacking activities.