Specifically, the Authority reported
For the present, our conclusion is that the engine failure was directly caused by low oil pressure.
In addition, the level of lubricating oil in the tanks was within set limits, yet relatively low, when the vessel started to cross Hustadvika. The tanks were provided with level alarms, however, these had not been triggered at this time.
The rough weather conditions and heavy seas most probably caused large movements in the tank, resulting to the supply of the lubricating oil pumps stopping.
NMA explained that the stop of the oil pumps triggered an alarm indicating a low level of lubrication oil, which in turn caused an automatic shutdown of the engines.
In the meantime, NMA permitted the vessel to voyage to Kristiansund where the necessary repairs would be made.
Viking Sky had 1.373 passengers onboard when it lost its engines. The vessel sent a mayday signal, triggering a massive evacuation mission which saw around 460 passengers airlifted by five helicopters.
The NMA alerted a general safety notice about ensuring a continuous supply of lubricating oil to engines and other critical systems in poor weather conditions.
Concluding, in light of this evidence, Viking Ocean Cruises replied
We have inspected the levels on all our sister ships and are now revising our procedures to ensure that this issue could not be repeated. We will continue to work with our partners and the regulatory bodies in supporting them with the ongoing investigations.