General Sikorski: photo - wikipedia
According to the Institute for National Remembrance (IPN), the state-backed body charged with investigating alleged crimes against Polish citizens, the probe will be the most comprehensive to date.
The Polish leader's death on 4 July 1943 remains a riddle to many, in spite of an official wartime investigation that claimed the crash was an accident.
Sikorski, who headed the Polish government-in-exile in London, was flying back to England after visiting Gibraltar when his Liberator plane plunged into the sea, shortly after take-off.
Apart from the pilot, who survived with broken limbs, all aboard apparently died immediately, although some bodies were never recovered, further fuelling conspiracy theorists.
Accusations have been levelled at Russia, Britain and a clique of Polish army officers over the years.
An official British military investigation blamed the crash on jammed controls in the cockpit.
As revealed in March this year by Piotr Dabrowski from IPN, besides archival work, two witnesses have been interviewed for the current probe in England and Spain.
The first was a radio operator who participated in the British navy's salvage operation, immediately after the plane went down. The second was a diver who helped extract bodies from the wreck.
Claims that Sikorski had been murdered prior to take off were largely dispelled following the exhumation of his remains in 2008 at Wawel Cathedral, Krakow.
Forensic tests ruled out that the general had been shot, stabbed or suffocated. The injuries were considered compatible with those suffered by victims of crashes.
Noted British historian Professor Norman Davies told the Krakow Post that “no reputable historian” had ever insisted that sabotage was the cause of Sikorski's death. (nh)