A Chinese nuclear submarine sank at a dock, the U.S. Department of Defense said.

According to U.S. Department of Defense officials, a Chinese nuclear-powered attack submarine sank at a dock under construction earlier this year, dealing a major blow to the Chinese military.

An official speaking to the BBC’s US partner CBS, speaking on condition of anonymity, said the loss of the submarine probably occurred between May and June.

Satellite images taken in June show what appears to be a rescue crane floating on a dock in Wuhan, where the vessel was spotted a month ago. Beijing has not confirmed the report.

U.S. officials said they were “not surprised” that the Chinese military covered up the loss of one of its newest assets.

It is unclear whether nuclear fuel was loaded on the submarine at the time.

A Chinese Foreign Ministry spokesman said Friday he was not familiar with the subject and did not provide any information when asked about it at a Beijing news conference.

This incident raises questions about China’s defense industry, which is rife with corruption.

china It has the largest navy in the worldIt has a fleet of more than 370 ships and is currently producing the next-generation nuclear submarine, the Zhou class, the first of its kind.

Taiwan said it had conducted its own investigation into the submarine’s fate and had “obtained the situation through various intelligence and surveillance methods,” but did not provide further details.

Thomas Shugart, a former U.S. Navy submarine crew member and analyst at the Center for a New American Security, first discovered the submarine-related incident last July.

He told the BBC that the sinking was a “setback” that would cause “quite significant embarrassment” for the People’s Liberation Army (PLA) navy, but that the safety risk was “probably very low.”

But he added: “If this ship is repaired, and I am confident it will be, it will be a much more capable submarine than any of the previous shipyards built.”

“I don’t see that as significantly changing the really impressive upward trajectory of PLA naval capabilities.”

The sinking comes as China increasingly asserts its rights. Virtually the entire South China SeaThis is very important for international trade.

It has long-standing maritime disputes with other countries in the region, including Brunei, Malaysia, the Philippines, Taiwan and Vietnam.