WARSAW--Polish military prosecutors on Friday charged Polish and Russian officials with causing an airplane crash that killed President Lech Kaczynski and 95 others in 2010, while admitting the crew of the plane was mainly to blame.

The investigators broadly confirmed earlier findings by the Polish administration concluding that bad weather, mistakes by the Polish Air Force detachment in charge of transporting the president, and errors by Russian air-traffic controllers all contributed to the accident.

After a nearly five-year-long investigation the prosecutors charged Polish officials with inappropriate selection of the flight crew, who lacked the qualifications and experience needed to fly the presidential plane in difficult weather conditions. The Russian flight controllers from Smolensk are being charged with putting the plane at risk and unintentionally causing the crash. Details of the accusations are being withheld.

The Polish officials have denied the accusations and declined to provide explanations for their actions, Prosecutor Ireneusz Szelag said.

Mr. Szelag said steps have been taken to interrogate the Russian controllers, who face up to eight years in prison if tried and found guilty.

"It is not our role to estimate chances for these men coming to Poland," Mr. Szelag said.

Relations between Warsaw and Moscow have deteriorated since the crash, with Polish officials making numerous complaints about Russia's actions in its aftermath. The airplane wreckage remains in Smolensk five years after the tragedy despite repeated requests by the Polish government for its return.

Polish-Russian relations turned soured further following the ousting of Ukraine's president Viktor Yanukovych, Russia's annexation of the Crimea and the resulting separatist conflict in the east of the country.

Warsaw is a vocal supporter of Kiev's new regime and opposed Russia's actions both in the Crimea and eastern Ukraine and has frequently called on the European Union to impose tougher sanctions on Moscow.

The prosecutors" decision, which was taken two weeks before the fifth anniversary of the crash and during a continuing presidential campaign, is likely to rekindle internal Polish conflict between supporters of the conservative Law and Justice party and the ruling Civic Platform.

Law and Justice supporters, often distrustful of Moscow, believe the government isn't doing enough to explain the crash and say no cause should be ruled out, including a potential plot to assassinate President Kaczynski.

Write to Patryk Wasilewski at patryk.wasilewski@wsj.com

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