The breaches took place in January and February, US officials told the Washington Post, speaking on condition of anonymity about an ongoing investigation led by the Navy and assisted by the Federal Bureau of Investigation.
Chinese government hackers compromised the computers of a U.S. Navy contractor and stole a large amount of highly sensitive data on undersea warfare, the Washington Post reported on Friday, citing unnamed U.S. officials.
The stolen data included secret information about a project known as Sea Dragon, as well as cryptographic systems and the Navy submarine development unit's electronic warfare library, the paper reported.
While the information was stored on the contractor's unclassified network, it was described as "highly sensitive" in the Post report.
The Navy and FBI are investigating the breach. Bill Speaks was quoted as telling the Post.
'It would be inappropriate to discuss further details at this time, ' they added.
The data that was compromised by what officials believe were Chinese hackers working for the state intelligence agency concerns the Sea Dragon project, which is aimed at "integrating an existing weapon system with an existing Navy platform".
It did not provide any specifics on the project, saying it was asked by the Navy to withhold the details from the report, so as not to damage USA security further.
The breach continues China's longstanding effort to "blunt the USA advantage in military technology and become the pre-eminent power in east Asia", the Post reported.
The news comes days before a summit in Singapore at which US President Donald Trump will meet North Korean leader Kim Jong-un, who counts Beijing among his allies.
According to the Post, the Sea Dragon project was created by the Pentagon in 2012 to adapt existing USA military technologies to new applications.
The investigation into the breach, which is being jointly conducted by the Navy and the FBI, is now underway, The Post reported.
Military experts said the breach signaled that China could be working to complicate the Navy's ability to defend US allies in Asia amid a conflict with Beijing in the region.