China’s newest nuclear-powered submarine, the first of its Zhou-class line, sank pierside in the spring, with the Chinese Navy attempting to conceal the incident, according to U.S. defense officials.

The submarine, recognized by its X-shaped stern, disappeared from satellite images after March. The loss was first noticed due to unusual crane activity at the shipyard.

China prioritizes the modernization of its navy, aiming to rival the U.S. military. It’s unclear if the submarine was loaded with nuclear fuel, CNN has reported.

The incident raises concerns about oversight and accountability in China’s defense industry.

Written by B.C. Begley