Polish security officials say Belarus committed an act of "state terrorism" by diverting a flight to Minsk to arrest an exiled journalist.
A Polish investigation into the plane diversion has refuted Belarus' claim that there was an alleged bomb threat on board.
The Ryanair flight was traveling from Greece to Lithuania when it was ordered to land in Minsk in May.
Opposition figure and journalist Roman Protasevich was then removed from the plane and detained alongside his partner. He remains under house arrest in Belarus.
The incident led the European Union and others to impose sanctions on the regime of Belarusian president Alexander Lukashenko.
Poland’s Internal Security Agency and prosecutors launched an investigation into the flight diversion, as there were 125 Polish citizens on board the aircraft. The Ryanair plane was also registered in Poland.
A security services spokesperson, Stanislaw Zaryn, said the probe had found no evidence of a bomb threat.
Zaryn added that Belarusian security officers were at the Minsk air traffic tower where they gave a controller instructions to order the plane to turn back and land.
The spokesperson added that the diversion was aimed at detaining a “political opponent of the regime of Alexander Lukashenko” and can be considered an “act of state terrorism.”
At a press conference on Friday, Polish officials played a recording of an apparent conversation between the Ryanair pilot and Belarusian air traffic controllers.
The pilot can be heard asking where the bomb threat information came from and then being told the source was Belarusian special services.
Belarus has maintained that the plane was diverted after they received a warning that a bomb was on the plane.
But Poland’s investigators said an email with the alleged threat was sent around 30 minutes after the controller relayed the initial message to the pilot.
European leaders had previously called the Belarus plane diversion a "hijacking" and banned Belarusian airlines from flying in EU airspace.