PERM, Russia (Reuters) -- Russian forensic scientists have begun to try to identify the remains of 88 people killed when an Aeroflot Boeing 737 crashed in a ball of fire near the Ural mountains.
Officials have said engine failure caused the September 14 crash, dismissing fears terrorists had attacked the airliner.
Flags flew at half-staff for a day of mourning in the Russian city of Perm where the plane came down, killing all passengers and crew.
Distressed relatives had been asked to give blood tests to help identify the victims through DNA tasting.
President Dmitry Medvedev held a minute of silence at a Kremlin meeting.
"Before we start, yesterday we had a tragedy, a plane crashed and people died and I would like to honor their memory," Medvedev said.
Relatives were due to visit the crash site as investigators sifted though the remains of the shredded fuselage, which rescue workers said was smashed into more than a thousand pieces.
"My wife woke me up and said, 'You are not going to go back to sleep after what I am going to tell you -- the radio is saying the plane from Moscow has crashed,'" one man who lost his son in the crash was shown saying on television. He then wept.
Some relatives were taken to hospital with shock. All have been given the chance to speak to psychologists.
The plane, flying from Moscow and operated by an Aeroflot subsidiary, disappeared from radio contact in the early hours of September 14 and crashed half an hour later. The city is around 1,340 kilometers east of Moscow, a flight time of just under two hours.
"Different causes are being looked at, but at present, the main lead is the technical failure of the aircraft," Russian news agencies quoted a spokesman for the Prosecutor-General's main investigative unit as saying.
Russia's domestic intelligence agency, the FSB, said there was no evidence that explosives could have played a role in downing the aircraft.
Aeroflot said 21 foreign nationals were among the dead -- nine from Azerbaijan, five from Ukraine and one from France, Switzerland, Latvia, the United States, Germany, Turkey, and Italy.
Russian news agencies said one of the dead was General Gennady Troshev, who in 2000 commanded the Russian Army against separatist rebels in the north Caucasus region of Chechnya.
Russian media quoted witnesses as saying they saw one of the engines on fire as the plane tumbled through the air and eventually hit the ground at a 45-degree angle. Traffic controllers said the pilot had not followed instructions in the last conversations before radio contact was lost.
Russian aviation has been trying to shake off its patchy safety record since the fall of the Soviet Union.
The crash was the worst since 170 people died in August 2006 when a TU-154 plane crashed in Ukraine on a flight from the Black Sea resort of Anapa to St. Petersburg.
The last Aeroflot plane crash occurred in March 1994 in Siberia when 70 people were killed. Investigators found that the pilot's teenage son had been allowed to enter the flight cabin and had accidentally switched off the autopilot.