Authorities are unsure of what caused the accident and the victims have not yet been identified, but they are believed to be three men from Lower Saxony on a return trip from Poland.
Because the Socata TB 20 plane was a four-seater, police were initially looking for traces of a possible fourth victim, but ended their search early on Thursday morning.
According to initial findings, the plane was stored at the Klausheide airport when not in use.
