North Korea has detained another official over last week’s failed launch of a warship, which damaged the 5,000-ton naval destroyer, state media reported Monday.

Pyongyang announced “a serious accident” at Wednesday’s launch ceremony, which crushed sections of the bottom of the newly built destroyer.

North Korean leader Kim Jong Un called the mishap a “criminal act caused by absolute carelessness”.

Ri Hyong Son, vice department director of the Munitions Industry Department of the Party Central Committee, was summoned and detained Sunday, the Korean Central News Agency reported.

He was “greatly responsible for the occurrence of the serious accident”, it said.

Ri is the fourth person reportedly detained in connection with the accident, following the detention of three individuals over the weekend, including the chief engineer at the shipyard.

KCNA reported on Friday that shipyard manager Hong Kil Ho had been summoned by law enforcement

“At the scene of the destroyer launch accident, the work for completely restoring the balance of the warship is being actively conducted,” KCNA said, adding that it is being done “according to its schedule.”

South Korea’s military said that Washington and Seoul’s intelligence authorities had assessed that North Korea’s “side-launch attempt” of the ship failed, and the vessel was left listing in the water.

KCNA, however, reported that an “underwater and internal inspection of the warship confirmed that, unlike the initial announcement, there were no holes made at the warship’s bottom” and called the extent of the damage “not serious.”

The South Korean military estimated that, based on its size and scale, the newly built warship is similarly equipped to the 5,000-ton destroyer-class vessel Choe Hyon, which North Korea unveiled last month.

Pyongyang has said that Choe Hyon is equipped with the “most powerful weapons”, and that it would “enter into operation early next year”.

Seoul’s military has said the Choe Hyon could have been developed with Russian help, possibly in exchange for Pyongyang deploying thousands of troops to help Moscow fight Ukraine.