MOSCOW, October 9 (RAPSI) – Chief Military Prosecutor Office in Poland extended the investigation of President Lech Kaczynski’s plane crash by 6 months till April 10, 2016, RIA Novosti reported on Friday.

The investigation timetable of this incident is regularly extended each six months.

According to the investigators, this case lists more than 650 open documents and 120 closed ones.

A Polish Tu-154 plane carrying then President Lech Kaczynski, his wife, and a large group of high-ranking officials crashed near Smolensk due to thick fog on April 10, 2010, killing 96 people.

The Moscow-based Interstate Aviation Committee issued a final report in late July 2011, saying that the crew’s decision not to divert to an alternate airfield was a direct cause of the plane crash. Other causes were inadequate flight operations and training standards.

Poland, which carried out a separate investigation, blamed the Russian air traffic controllers for the tragedy.