The US Navy has figured out what a nuclear-powered attack submarine ran into in the South China Sea

• The US Navy has completed its investigation into a submarine incident in the South China Sea.
• The USS Connecticut ran aground on an uncharted seamount, USNI News first reported.

US Navy investigators have determined what a nuclear-powered attack submarine hit in the South China Sea last month, USNI News reported Monday, citing defense officials familiar with the investigation and a legislative official.

The Seawolf-class nuclear-powered attack submarine USS Connecticut collided with an unidentified object on October 2, the Navy said five days after the incident. Investigators have determined the submarine ran aground on an undersea mountain, the location of which was previously unknown, USNI News said.

The 7th Fleet confirmed the USNI News report to Insider, with its spokesperson Cdr. Haley Sims saying: "The investigation determined USS Connecticut grounded on an uncharted seamount while operating in international waters in the Indo-Pacific region."

The earlier Navy statement on the incident left a lot to the imagination. It said the submarine struck something while operating in international waters, there were no life-threatening injuries, the submarine was in stable condition, and the nuclear-propulsion systems were not damaged.

The sea service did not say where the incident occurred, though Navy officials speaking on the condition of anonymity told some reporters it happened in the South China Sea after the release of the statement.

As of Wednesday, the US Navy was not quite sure what the submarine hit, though defense officials told USNI News that early indications suggested that the Connecticut crashed into a seamount, an undersea mountain that rises from the ocean's depth. Those can also pose a risk to ships on the surface, depending on how close its summit is to the surface.

China, often at odds with the US in the South China Sea, has capitalized on the limited information provided by the Navy about the incident, with Chinese officials accusing the US of a cover-up and calling it "cagey" and "irresponsible."

The US military denied it was trying to cover up the incident. After a Chinese Foreign Ministry spokesperson first made the allegations, Pentagon press secretary John Kirby said, "It's an odd way of covering something up when you put a press release out about it."

But Beijing, both the foreign ministry and the defense ministry, has continued to criticize the US for a "lack of transparency," while repeatedly calling the US "the biggest force for militarization of the South China Sea," an accusation typically directed at China.

The conclusion of the command investigation into the Connecticut incident takes some of the mystery out of things. The investigation has been passed up to the 7th Fleet commander, who will make decisions about accountability actions, a fleet spokesperson said.

As the investigation into the incident has not yet been publicly released, information is still limited on how the submarine ran into a seamount and to what degree members of the crew and command were responsible.

The submarine, one of only three in the powerful Seawolf class, is in Guam, where it is undergoing repairs, likely initial work before more extensive repairs can be completed elsewhere.

There are concerns that if the Connecticut had to be taken back to a public shipyard for additional repairs, it could throw a wrench into a submarine-maintenance backlog that has long been problematic.

Update: This report has been updated with comment from 7th Fleet.