A Polish investigation has found no evidence of foul play in the plane crash that killed Gen. Wladyslaw Sikorski, Poland's leader in exile, in 1943.

Sikorski was serving in that role in London during World War II when he died in a mysterious plane crash just after takeoff from Gibraltar. A British investigation blamed the crash on a blocked rudder, but Sikorski's dispute with Soviet leader Joseph Stalin that year led to speculation of an assassination.

Poland's National Remembrance Institute opened an investigation in 2008 to check for a possible Soviet-instigated crime. It examined the bodies of Sikorski and three others killed in the crash, questioned witnesses and examined old files.

Andrzej Arseniuk, a spokesman for the investigators, said Monday the probe found no proof of a crime.