Two people were killed on Friday morning after their helicopter, which was spraying insecticides, crashed into the Schinias wetland in Marathon in northeastern Attica.
Two people were pulled out of chopper by rescue crews but were pronounced dead soon after.
A third person in the helicopter was reportedly injured lightly.
It remained unclear what caused the crash.
According to the fire brigade, the helicopter was privately craft and had been hired by regional authorities to spray insecticide in order to control mosquito populations.