Grieving relatives of 96 people killed in the Polish presidential air disaster were in Russia on Monday to carry out the grim task of identifying corpses, many of them disfigured beyond recognition.
President Lech Kaczynski's body was taken back to Warsaw on Sunday but that of his wife and dozens of other victims of the crash have still not been identified, Polish and Russian officials said.
Russia -- which over the past years has had tense relations with Poland -- was holding an official day of mourning for the crash victims with flags flying at half mast and entertainment programmes cancelled.
Russian officials have stated that there was no technical fault with Kaczynski's Russian-built plane and that the Polish pilots were flying too low when they tried to land in thick fog on Saturday.
A special flight from Warsaw carrying the first of the relatives arrived in Moscow overnight and a second plane was expected to land in the course of the day, officials said.
The relatives, who are being put up in hotels in the capital, were starting the identification process at Moscow's municipal morgue number three where the corpses are being held.
One hundred and thirty-two relatives have already arrived in Moscow.
The Polish military chief of staff and heads of the main armed services were also on the crashed plane along with the central bank governor, two deputy ministers, lawmakers and religious and cultural officials.
"The procedure for the relatives to identify the corpses is starting," said Russian Health Minister Tatyana Golikova, standing alongside her Polish counterpart, Ewa Kopacz.
"We think that this procedure will last 2-3 days. We will do everything so this work is organised well and quickly," said Golikova, adding that psychologists from Poland and Russia were helping the relatives in the ordeal.
Kopacz said the procedure would be difficult and some of the bodies were so badly disfigured that they could only be identified with the help of DNA evidence.
Russians paid their respects to the dead by laying flowers and candles outside the Polish embassy in Moscow. "Grief without borders," headlined the pro-government Izvestia newspaper.
Kaczynski and the presidential delegation died as they were heading to a memorial service at Katyn, near Smolensk, for 22,000 Polish officers and troops killed in World War II 70 years ago.
Russian investigators on Sunday ruled out a technical fault with the Tupolev Tu-154 jet. Though it was an ageing Soviet-built craft, the jet had undergone a major overhaul in December, the Russian makers said.
"The recordings that we have confirm that there were no technical problems with the plane," Russia's chief investigator Alexander Bastrykin told Prime Minister Vladimir Putin who is leading an official inquiry.
Recordings of the plane's communications with air traffic control revealed the pilot had been warned that thick fog over the airport created dangerous conditions, but tried to land anyway, Bastrykin said.
"The pilot was informed about complex weather conditions but nevertheless made a decision to land," Bastrykin, the head of Russia's investigative committee said.
