Mitsubishi Heavy Industries Ltd.'s computer network was hacked at factories that build submarines, missiles and components for nuclear power plants in the first such attack targeting Japan's defense industry, the Yomiuri newspaper said Monday.

Information from the company's computer system was stolen in the cyber attack, the Yomiuri said without citing where it got the information.

A Mitsubishi Heavy spokesman confirmed the cyber attack, but said the firm was still investigating the case including the possibility of information leaks.

Yomiuri said about 80 virus-infected computers were found at MHI's headquarters in Tokyo as well as manufacturing and research and development sites including Kobe Shipyard & Machinery Works, Nagasaki Shipyard & Machinery Works and Nagoya Guidance & Propulsion System Works.

The Kobe Shipyard currently builds submarines and makes components to build nuclear power stations, while the Nagasaki Shipyard makes escort ships. The Nagoya plant makes guided missiles and rocket engines, the paper said citing unnamed sources.