An Embraer Legacy 600 executive jet, believed to have carried Wagner mercenary chief Yevgeny Prigozhin to his death on Wednesday, showed no sign of problem until a precipitous drop in its final 30 seconds, according to flight-tracking data.

Rosaviatsia, Russia's aviation agency said Prigozhin, who led an aborted mutiny in June, was one of 10 people on board the downed plane. It was traveling from Moscow to St. Petersburg when it crashed near the village of Kuzhenkino in the Tver Region, Russia's emergency situations ministry said.

At 3:19 p.m. GMT, the aircraft made a “sudden downward vertical,” said Ian Petchenik of Flightradar24. Within about 30 seconds, the aircraft had plummeted more than 8,000 feet from its cruising altitude of 28,000 feet.

“Whatever happened, happened quickly,” Petchenik said.

“They may have been wrestling (with the aircraft) after whatever happened," Petchenik said. But prior to its dramatic drop, there was "no indication that there was anything wrong with this aircraft.”

Video showed the plane descending rapidly with its nose pointing almost straight downward and a plume of smoke or vapor behind it.

Russian investigators opened a criminal probe to determine what happened. Some unnamed sources told Russian media they believed the plane had been shot down by one or more surface-to-air missiles. Reuters could not confirm that.

Brazilian planemaker Embraer SA said it had not been providing any service or support in recent years to the plane, which seats around 13.

The company said in a statement it has complied with international sanctions imposed against Russia. The luxury jet was identified on Flightradar24 with registration RA-02795, the same as the plane that carried Prigozhin to Belarus after the mutiny, an industry source familiar with the matter said.

Online flight tracker Flightradar24 last recorded the position of the aircraft at 3:11 p.m. GMT, before the crash. Jamming or interference in the area probably slowed the collection of further location data.

Other data continued for nine minutes. Flightradar24 said the jet went thorough a series of ascents and descents of a few thousand feet each over 30 seconds before its final, disastrous plunge. Flightradar24 received its final data on the jet at 3:20 p.m.

Reuters