Polish military prosecutors have questioned more than 300 witnesses during their investigation into the April plane crash in western Russia that killed Poland's president, the country's attorney general said on Sunday.
Poland's PAP news agency reported that Andrzej Seremet said the evidence gathered in the case already ran to 62 volumes of documents.
Polish President Lech Kaczynski was killed on April 10 along with his wife an 94 other passengers and crew when their plane crashed while attempting to land in heavy fog at an airfield near the Russian city of Smolensk.
The top-level Polish delegation, which included dozens of senior military and civilian officials, were to attend a memorial ceremony marking the 60th anniversary of the 1940 Katyn massacre, in which Soviet secret police killed thousands of Polish military officers.
Kaczynski's twin brother, Jaroslaw, on Saturday called for the Polish government, including new President Bronislaw Komorowski and Prime Minister Donald Tusk, to resign over the investigation, accusing them of "completely abandoning" the probe.
Jaroslaw Kaczynski lost the presidential election to replace his late brother in a runoff against Komorowski.
The Polish attorney general praised the cooperation between the Russian and Polish sides in the investigation and said it would be stepped up following the awaited conclusion of a memorandum of cooperation.
"In October, we look forward to a representative of the Russian Prosecutor General's Office coming to Warsaw. Hopefully, a memorandum of cooperation will be signed," Seremet said.
WARSAW, September 12 (RIA Novosti)