Japan's space agency was likely hit by an unauthorized access attack on a network server, the government said Wednesday, adding that the incident did not involve sensitive information pertaining to rockets or satellites.

Sources close to the matter said the Japan Aerospace Exploration Agency (JAXA) was not aware that the breach may have occurred sometime during the summer until they were contacted by police this fall.

An official at the agency said no data leaks have been confirmed so far.

The government and relevant authorities are investigating the incident and are seeking to identify the source of the attack, the scope of the damage and any vulnerabilities in the agency's security systems.

JAXA was among the roughly 200 companies and research institutes hit by large-scale cyberattacks in 2016 and 2017, believed to have been conducted by a Chinese espionage group under the direction of the People's Liberation Army.

In April 2021, police referred a Chinese engineer to prosecutors on suspicion of signing a contract with a fake name to rent a server used in the attacks.

However, Tokyo prosecutors decided not to indict the man, a member of the Chinese Communist Party in his 30s, in October that year, without citing a reason.

JAXA was launched in 2003 through the merger of three space and aeronautical entities to handle the country's space programs, including satellite and rocket launches.