WARSAW (Reuters) - Polish prosecutors said on Monday they would press charges against two Russian air traffic controllers of deliberately contributing to a 2010 plane crash that killed Poland’s president and 95 other people.

Flowers are placed by a memorial stone during a remembrance ceremony at the site of the 2010 plane crash that killed former Polish President Lech Kaczynski and 95 others near the Russian city of Smolensk, April 10, 2013. REUTERS/Vasily Fedosenko

The crash near Smolensk in western Russia killed the Polish President Lech Kaczynski and his wife, as well as the central bank chief, top army commanders and several lawmakers.

An inquiry by the previous government returned a verdict of pilot error, but the ruling right-wing Law and Justice (PiS) party led by Kaczynski’s twin brother Jaroslaw, has said the crash may have been caused by an explosion on board.

The prosecutors said on Monday that a new analysis of recordings of conversations between the pilots and Russian controllers justified pressing the charges.

“An analysis of the evidence ... has allowed prosecutors to formulate new charges against air traffic controllers, citizens of the Russian Federation,” Polish Deputy Prosecutor General Marek Pasionek told a news conference.

Referring to the accusations, Kremlin spokesman Dmitry Peskov told reporters on Monday that circumstances of the tragedy have already been thoroughly studied and it was “certainly not possible to agree with such conclusions”.

Russia has so far refused to return the wreckage of the jet to Poland, a member of NATO and the European Union, citing its own continuing investigation.

The accusations of the Polish prosecutors, whom the PiS brought under direct government control, are likely to worsen relations with Moscow - already strained over the conflict in Ukraine - and increase tensions within Polish society.

The previous Polish government’s report indicated that Smolensk traffic controllers unintentionally contributed to the crash, charges Moscow had dismissed as false. A Russian report into the crash puts the blame squarely on the Poles.

The Polish prosecutors said on Monday that a re-opening of the victims’ coffins, which had been sealed in Russia, has revealed that in two cases remains were in the wrong coffins and in five coffins there were fragments of other bodies.

The crash was the worst such disaster in Poland since World War Two and left society deeply divided over its causes.

A transcript of conversations from the plane’s cockpit leaked by Polish media in 2015 showed that members of the president’s entourage urged the pilots to land despite heavy fog.

But many Poles were shocked with video footage showing Russian workers pushing around large parts of the wreckage with excavators, cutting cables and carelessly throwing smaller pieces into a heap on a truck.

The crash took place as pilots attempted to land a Soviet-made TU-154 at a rarely used airport near Smolensk to take part in commemorations of 22,000 Polish officers executed there by Soviet secret police in 1940.