MOSCOW — A passenger plane crashed Thursday in Russia’s Far East, killing all 48 passengers and crew on board, officials said.

The Angara Airlines flight disappeared from radar, and searchers later found the burning wreckage of the plane on a hillside south of its planned destination in Tynda, more than 4,350 miles east of Moscow, Russia’s Emergency Situations Ministry said.

Regional Gov. Vasily Orlov said in a statement that all 48 people aboard were dead, and announced three days of mourning in the Amur region over what he called a “terrible tragedy.”

It wasn’t immediately clear what caused the crash.

Russia’s Interfax news agency said there were adverse weather conditions at the time of the crash, citing unnamed sources in the emergency services. Several Russian news outlets also reported that the aircraft was almost 50 years old, citing data taken from the plane’s tail number.

The Soviet-designed twin turbo prop plane had initially departed from Khabarovsk before making its way to Blagoveshchensk on the Russian-Chinese border and onwards to Tynda.

Images of the reported crash site circulated by Russian state media show debris scattered among dense forest, surrounded by plumes of smoke.

Orlov said rescuers had struggled to reach the site due to its remote location, 9 miles south of Tynda.

An earlier statement from the governor said that 49 people had been onboard the flight, but that number later was updated to 48. The reason for the discrepancy was not immediately clear.

The transport prosecutor’s office in the Far East said in an online statement that the plane was attempting to land for a second time when it lost contact with air traffic control and disappeared from radars.

The authorities launched a probe on the charge of flight safety violations that resulted in multiple deaths, a standard procedure in aviation accidents.

Aviation incidents have been frequent in Russia, especially in recent years as international sanctions have squeezed the country’s aviation sector.