The floating dry-dock where Russian aircraft carrier Admiral Kuznetsov was being upgraded has ‘sunk completely’, damaging the vessel and potentially killing workers according to Russian media.

“The floating dock has already sunk completely,” a source told TASS. It was earlier reported that the floating dock sank partially.

According to latest reports, four people were seriously injured in the incident and another is reportedly missing.

The accident reportedly happened as the Admiral Kuznetsov was to be taken out of the dry dock. The ship has now been towed to the nearby Sevmorput Yard No 35, yard press spokesman Yevgeny Gladyshev told Interfax. He makes clear that a power outage was what caused the accident.

United Shipbuilding Corporation’s chief, Alexei Rakhmanov, said to state media:

“Obviously when a 70-ton crane crashes on the deck there could be damage, but preliminary reports show that the damage that the ship has suffered is not significant.”

There has been several cases of power outages all over the region recently, including in the cities of Severomorsk and Murmansk.

The carrier has a history of trouble. In November and December 2017, the carrier lost one Su-33 and one MiG-29KR, when both jets reportedly ditched into the sea. Problems with arresting gear were cited as the cause. In 2009, the aircraft carrier also lost a sailor when a fire broke out due to a short circuit.

The carrier started an overhaul and modernisation in the first quarter of 2017. This is expected to extend its service life by 25 years.