Traces of explosives were found on the fragments of Polish TU-154 plane that crashed on April 10, 2010, near Smolensk and killed then-Polish president Lech Kaczynski, his wife and 94 other top Polish officials, Polish daily newspaper Rzeczpospolita reports.
The TNT was discovered in recent tests conducted by "Polish prosecutors and experts," but AFP reports that testing by Polish and Russian investigator immediately after the 2010 crash had ruled out explosives.
The newspaper speculates there is a possibility that the TNT and nitroglycerine residue found on 30 seats may have come from an unexploded WWII shell.
However, government spokesman Pawel Gras told public broadcaster TVP that “We must wait for prosecutors to draw their conclusions and establish the source of the substance before taking any measures."
A Russian investigation found no evidence of foul play in the crash, but some people believe that Russia was behind the crash of the plane.
President Lech Kaczynski was very pro-American and a major promoter of former President George W. Bush's missile defense plan in Poland, which was opposed by Russia, former Bush administration National Security Council official Jamie Fly said.
A pilot error was suspected as a cause of the plane crash, and Russian officials says the plane was trying to land in thick fog and plane crashed on its second attempt. Conspiracy theorists also point to a video allegedly shot immediately after the plane crashed, in which shots seem to be heard.