Poland's opposition conservative party on Tuesday said it had not ruled out foul play, including terrorism, in the air disaster in Russia in April which killed its founder, president Lech Kaczynski.
"We're examining all the hypotheses, notably that of a terrorist attack," Law and Justice politician Antoni Macierewicz told reporters as he announced the launch of a parliamentary probe run by the party.
Macierewicz used the term "crime" to refer to the crash. He said he would elaborate when the probe had been wrapped up.
Kaczynski's official jet crashed as it tried to land in fog on April 10 in Smolensk, western Russia, killing all 96 people on board.
The victims, who also included first lady Maria Kaczynska, senior Polish politicians and military top brass, had been heading to a World War II memorial ceremony.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Initial findings from Russia's crash investigation have pointed to pilot error, but conspiracy theories have flourished on pro-Law and Justice websites.
Party leader and ex-prime minister Jaroslaw Kaczynski - the late president's identical twin - has accused Russia of stonewalling in the probe.
Macierewicz, of the conservatives' hardline nationalist wing, was the minister responsible for the intelligence services in Jaroslaw Kaczynski's cabinet which lost office in a 2007 general election.
Earlier this month, Jaroslaw Kaczynski failed to replace his brother as head of state after losing in a run-off election against Bronislaw Komorowski of the governing liberal Civic Platform.
Politicians from the Civic Platform and the left-wing opposition Social Democrats boycotted Tuesday's founding session of the parliamentary probe group.
"The goal of this group is simply to create myths that will serve as a political springboard ahead of the upcoming elections," Civic Platform politician Marek Biernacki told the rolling news channel TVN24.
Poles are due to vote in municipal elections later this year, before a parliamentary ballot in 2011.
"This group will serve simply to foster political emotion," said Social Democrat politician Stanislaw Wziatek.
Justice Minister Krzysztof Kwiatkowski underlined that such parliamentary groups lack formal powers.
