A pilot escaped unscathed after the firefighting helicopter he was flying plunged into a lake in Lamoso, Paços de Ferreira, on Monday.
The helicopter was refilling its water tanks to help put out a fire in the nearby area of Sanfins.
It is unclear how the helicopter ended up in the water, but the pilot was able to get out unharmed before it sunk.
According to the pilot, there was no sign of mechanical failure before the accident, a source from Heliportugal, the company responsible for the government’s helicopters, told Público newspaper.
The causes of the accident are being investigated.
The helicopter is expected to be retrieved from the bottom of the lake today.