The floating dock where Russian aircraft carrier Admiral Kuznetsov was being upgraded, has sunk completely, a source in emergencies services told TASS on Tuesday.

"The floating dock has already sunk completely," the source said. It was earlier reported that the floating dock sank partially.

According to latest reports, four people were injured in the incident, one of them is in serious condition. The Admiral Kuznetsov was towed to another shipyard in Murmansk.

"Despite an emergency, the Admiral Kuznetsov was floated. The schedule for its repairs was not disrupted," spokesman for the Zvezdochka shipyard Yevgeny Gladyshev said.

The operation to recover the sunken floating dock PD-50 in Murmansk will be rather tricky and may take six months to one year to accomplish, a source in the defense-industrial complex has told TASS.

"The enormous size and displacement of the floating dock as they are, the operation to recover it will be rather tricky. A great deal will depend on whether it lies flat or on the side. The moment it sank the floating dock developed a list, so most probably it is on the side, which will complicate the operation. The experience of recovering a sunken nuclear submarine (The Kursk) indicates, that the operation to recover the floating dock may take at least six months or last for a whole year," the source said.

Apart from the PD-50 Russia has another floating dock, PD-1, of approximately identical parameters in Severodvinsk. It is capable of accommodating large surface ships, such as The Admiral Kuznetsov or The Pyotr Veliki.

The floating dock of the 82nd repair plant in Murmansk sank the moment The Admiral Kuznetsov was being pullout out. Four workers suffered hypothermia and were taken to hospital. One of them also had a stomach injury. One person went missing.

The first video has emerged from the location where a floating dock holding Russian aircraft carrier Admiral Kuznetsov became submerged overnight Tuesday.

The clip opens with a view of dry dock PD-92, which is around four times smaller than the sunken PD-50. The latter was previously floating on the left, but now is completely submerged in water after a power supply disruption caused its pumps to break down, overloading its cisterns with water.