Grieving relatives visited the scorched site of a passenger jet crash Thursday to identify the 170 people killed in the third airline disaster this year in the former Soviet Union.

Some 140 relatives traveled in a bus convoy to the crash site near the Ukrainian city of Donetsk, where they were met by medical personnel and an Orthodox priest in long black robes. The families gathered near a large wooden cross with a sign reading: "Donetsk Grieves." Many appeared to be praying silently.

Investigators are focusing on weather conditions, including lightning and turbulence, as the possible cause for Tuesday's crash, which killed all those aboard the Russian airliner, including 45 children. The plane had been flying from Anapa — a holiday destination on the Russian Black Sea coast — to St. Petersburg.

CountryWatch: Russia

The pilot sent repeated distress signals during a severe thunderstorm before the Pulkovo Airlines' Tu-154 disappeared off radar screens.

Experts combing the site found 171 bodies and one fragment, said Russia's Transport Ministry spokeswoman Svetlana Kryshtanovskaya. She couldn't explain the discrepancy with the flight list — which registered 160 passengers and 10 crew — saying expert analysis would be required.

Transport Minister Mykola Rudkovsky said the identification process would begin later Thursday — first by showing the family members photographs of remains, and then taking them to the morgue. Many would be asked to give blood samples for DNA analysis, he said.

Ukraine scaled back celebrations Thursday to mark its Independence Day. Russia was also marking Thursday as a day of mourning, with flags flying at half-staff.

The two flight recorders, which were found Wednesday, were sent to Moscow. Experts have ruled out terrorism in the crash.

The storm Tuesday brought heavy wind and rain to the Donetsk region, 400 miles southeast of Kiev, temporarily knocking out power to some residents and turning the sky so dark that street lights automatically switched on.

Other officials suggested the plane might have been struck by lightning, or hit strong turbulence, causing the 39-year-old pilot to lose control.

The crash was the third in Russia or involving a Russian airline this year, raising concerns about the flight-worthiness of the civilian air fleet in the ex-Soviet Union. Following the 1991 collapse of the Soviet Union, hundreds of airlines, often underfunded and poorly managed, were spun off from state airline Aeroflot and the region became plagued by crashes.

However, there had been few crashes in the past five years and many airlines began acquiring Western-made planes to replace deteriorating Soviet-made planes. The other two fatal crashes this year, both in Russia, involved Airbus planes.

The Tu-154 that crashed Tuesday was 16 years old.