The chief of the Wagner Russian mercenary group, Yevgeny Prigozhin, is believed to have been killed in a plane crash, Russian state media reported Wednesday.

The aircraft, a business jet, crashed in the Tver region northwest of Moscow, leading to the deaths of all 10 people onboard, according to Russian authorities.

While Russian officials said that Prigozhin was on the passenger list, it was not immediately clear if he was in the aircraft.

“An investigation of the Embraer plane crash that happened in the Tver Region this evening was initiated. According to the passenger list, first and last name of Yevgeny Prigozhin was included in this list,” Russia’s Federal Agency for Air Transport said in a statement.

The plane was flying from Sheremetyevo International Airport in Moscow to St. Petersburg, the agency said, according to a Google translation.

The Russian Ministry of Emergency Services wrote on its Telegram account: “In the Tver region, near the village of Kuzhenkino, a private Embraer Legacy aircraft crashed while flying from Moscow to St. Petersburg. There were 10 people on board, including 3 crew members.”

“According to preliminary information, all on board were killed. EMERCOM of Russia is conducting search operations,” the post read, according to a Google translation.

U.S. President Joe Biden has been briefed on the situation, a White House spokesperson told NBC.

National Security Council spokesperson Adrienne Watson said that, if confirmed, Prigozhin’s death should come as no surprise.

“We have seen the reports. If confirmed, no one should be surprised,” Watson said. “The disastrous war in Ukraine led to a private army marching on Moscow, and now — it would seem — to this.”

U.S. Secretary of State Antony Blinken also commented on the developing situation.

“The fact that Prigozhin made a direct challenge to Putin’s authority, the fact that he questioned publicly the very premises that Putin has advanced for the aggression against Ukraine – that’s playing out and will continue to play out,” Blinken told MSNBC’s Andrea Mitchell on Wednesday when asked about the incident.

“We’ve seen the ongoing drama, too, of where is Prigozhin, what is the arrangement with Putin?” he added. “If I were Mr. Prigozhin, I would remain very concerned. NATO has an ‘Open Door’ policy; Russia has an open windows policy, and he needs to be very focused on that.”

The “open windows policy” was a tongue-in-cheek reference to the fact that numerous prominent Russian officials and businessmen who fell out of favor with Putin died by what local authorities described as falling out of windows or off of balconies.

Prigozhin effectively disappeared from public life after the failed mutiny. But just on Monday, Aug. 21, the mercenary leader appeared in a video published by Wagner-affiliated channels on Telegram, which suggested the footage was filmed in Africa. It was believed to be Prigozhin’s first video address since the coup attempt.

In the clip, the Wagner leader is holding a rifle and standing against a desert backdrop. The camera briefly pans to other armed men in a pickup truck.

“We are working. The temperature is plus 50 [Celsius]. Everything’s the way we like it. PMC Wagner is conducting reconnaissance, making Russia even greater on every continent – and Africa even freer,” Prigozhin said, according to a NBC News translation.

“Justice and happiness for the African nations,” he said. “We are messing with ISIS, Al-Qaeda and other banditos. We hire real supermen and continue working on tasks that were set to us and we promised to carry out.”

NBC News was not able to verify the video’s authenticity, as well as when or where it was shot.

Wagner has operated in parts of Africa including Mali, the Central African Republic and Libya.