Pilot error may be to blame for a plane crash in western Russia on Saturday that killed the Polish president and 95 other people, Russian investigators say.

President Lech Kaczynski and his wife, along with dozens of high-ranking government and defence officials, died when their Tu-154 plane crashed in heavy fog near Smolensk, Russia.

Russia's chief investigator, Alexander Bastrykin, said Monday that investigators have almost finished reading the flight recorders.

"The readings confirm that there were no problems with the plane, and that the pilot was informed about the difficult weather conditions, but nevertheless decided to land," Bastrykin said during a briefing with Russian Prime Minister Vladimir Putin in Smolensk.

The Polish delegation was travelling to Russia to attend a memorial for more than 20,000 Polish soldiers, police and others executed by the Soviet secret police and buried in mass graves in the Katyn Forest near Smolensk in 1940.

People place flowers next to wreckage near Smolensk, in western Russia, where the plane carrying the Polish president and 95 others crashed. (Mikhail Metzel/Associated Press)The pilot was identified as Capt. Arkadiusz Protasiuk, 36, and the co-pilot as Maj. Robert Grzywna, 36. Also part of the cockpit crew were Ensign Andrzej Michalak, 36, and Lt. Artur Zietek, 31.

In Warsaw, there was speculation the aircrew may have been asked by someone in the plane to land at Smolensk — instead of being diverted to Minsk or Moscow — in part to avoid missing the commemoration ceremonies.

President to lie in state

Thousands of people lined the streets of Warsaw on Sunday as the hearse carrying the 60-year-old Kaczynski's body arrived in the capital, where it will lie in state starting Tuesday. On Monday, crowds gathered at the presidential palace to mark the beginning of a week of mourning.

"We want every Pole who wants to pay tribute to the president to be able to come and stand by the coffin," said Jacek Sasin, a spokesperson for the presidential palace.

Sasin said officials are planning to hold a state funeral Saturday but a final decision depends on when the bodies of all the passengers are identified and returned to Poland.

Bronislaw Komorowski, the acting president, said Monday that plans are being made to call a new election. He also said the government will review the rules that allowed so many senior officials to travel in the same plane.

In Canada, members of the Polish community were mourning the crash victims. In Toronto, people laid flowers at the Katyn Memorial at King Street and Roncesvalles Avenue in the city's west end. In Vancouver, hundreds of mourners gathered at St. Casimir's Polish Parish in East Vancouver on Sunday for a mass and memorial service.

With files from The Associated Press