The Chinese government reportedly covered up the sinking of its newest nuclear-powered submarine as it sat tied to a pier, and U.S. officials say it is no surprise.

"It’s not surprising that the PLA Navy would try to conceal the fact that their new first-in-class nuclear-powered attack submarine sank pierside," a senior U.S. Defense official said. "In addition to the obvious questions about training standards and equipment quality, the incident raises deeper questions about the PLA’s internal accountability and oversight of China’s defense industry, which has long been plagued by corruption."

China’s first Zhou-class submarine likely sank between May and June, The Associated Press reported based on information from an official who spoke on condition of anonymity. Satellite images showed cranes in the area that would have been necessary to salvage the vessel from the bottom of the river.

The incident reportedly forced Chinese authorities to rush to cover up the matter, which had not been previously disclosed.

CHINA'S NEW ROLE FOR ITS NUCLEAR SUBMARINES HAS THE PENTAGON'S ATTENTION

Visitors walk on the decks of decommissioned submarines at the PLA Naval Museum in Qingdao, China. (Kevin Frayer/Getty Images)

China has previously said it is building a world-class military so it can deter aggression and protect its overseas interests.

Last year, the Pentagon announced it had discovered in a little-known report that China’s military adopted a policy of keeping at least one nuclear-capable submarine at sea at all times.

China maintains a fleet of six nuclear-capable submarines, carrying missiles that could hit the continental U.S. from the South China Sea.

AUSTRALIA COMMITTED TO BUILDING SUB FLEET POWERED BY US NUCLEAR TECH DESPITE CRITICISM FROM FRANCE

China has adopted a policy of having at least one nuclear-capable submarine deployed at sea at all times, straining U.S. resources. (Dana Jensen/The Day via AP, File)

The report on China's new submarine activity came just as the U.S., U.K. and Australia entered an agreement for the production and sale of nuclear-powered attack submarines. Australia was also expected to purchase the vessels to modernize its fleet.

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The attack submarines are prime candidates for tracking missile submarines like those China has deployed, and increasing Australia's capabilities will take some pressure off U.S. and U.K. forces in the region.

Fox News Digital’s Anders Hagstrom and Reuters contributed to this report.