MOSCOW (Reuters) - Russia rejected on Thursday Polish accusations that it mishandled the remains of former president Lech Kaczynski and other Polish dignitaries who died in a 2010 plane crash in Russia that killed all 96 on board.

Polish authorities said last week they had found the remains of two other people in Kaczynski’s coffin while examining the exhumed coffins of victims from the plane crash, which occurred near the western Russian city of Smolensk.

The caskets of 11 further victims also contained body parts of others, prosecutors said after examining 24 coffins from the crash.

“Such accusations are absolutely unfounded,” Russian Foreign Ministry spokeswoman Maria Zakharova told a news briefing.

Back in 2010, Moscow was under pressure from Warsaw to “hand over the remains as soon as possible”, Zakharova said.

“The de-facto identification of the remains was conducted by forensic experts expeditiously on April 11-12 (2010). Besides, the identification of the bodies was done directly by Polish representatives and relatives of the dead.”

The April 2010 crash - the worst such disaster for Poland since World War Two - has left Polish society deeply divided over the cause despite the previous government’s conclusion from its own investigation that pilot error had been to blame.

Poland’s current government under the Law and Justice (PiS) party, led by Lech Kaczynski’s twin brother Jaroslaw, took direct control of the prosecutor’s office and moved to re-examine the Smolensk crash after taking power in late 2015, saying the previous investigation was not conducted properly.

Some officials of the ruling right-wing party have blamed the tragedy on an explosion aboard, without providing evidence.

Polish Deputy Prosecutor General Marek Pasionek told reporters last week that in 12 of 24 coffins reopened since last year, bodies had been swapped in two, one contained half the body of another person, while nine other caskets held scattered remains of other victims.

Zakharova said that when identification was impossible, the remains were handed over to Poland with numbers assigned to them. “It is also no less important that the bodies were put in the coffins in the presence of the Polish side,” she said.

“Russia cannot bear responsibility for what was happening to these remains on their return to Poland. This is already a matter for the Polish side to deal with.”

The Moscow-based Interstate Aviation Committee (MAK) reaffirmed on Thursday that the disaster had been caused by human error.

The crew was landing “despite lacking visual contact with orienting points on the ground below a safe altitude of 100 meters”, RIA news agency cited Alexei Morozov, the head of MAK’s technical commission that investigated the crash, as saying.

MAK, which comprises 12 ex-Soviet nations, is charged with upholding safety and conducting independent air accident investigations in their common airspace.