A preliminary U.S. intelligence assessment concluded that an intentional explosion caused the plane crash presumed to have killed a mercenary leader, as suspicions grew over a Kremlin-orchestrated assassination.

One of the U.S. and Western officials who described the initial assessment said it determined that Yevgeny Prigozhin was "very likely" targeted and that the explosion falls in line with Vladimir Putin’s "long history of trying to silence his critics."

The officials, who spoke on the condition of anonymity because they were not authorized to comment, did not offer any details about what caused the explosion, which was widely believed to be vengeance for the mutiny in June. Several of Prigozhin's lieutenants were also presumed dead.

Pentagon spokesperson Gen. Pat Ryder said press reports that a surface-to-air missile took down the plane were inaccurate. He declined to say whether the U.S. suspected a bomb or believed the crash was an assassination.

Details of the intelligence assessment surfaced as Putin expressed his condolences to the families of those who were reported to be aboard the jet and referred to "serious mistakes" by Prigozhin.

The jet carrying the founder of the Wagner military company and six other passengers crashed Wednesday soon after taking off from Moscow with a crew of three, according to Russia's civil aviation authority.

Rescuers found 10 bodies, and Russian media cited anonymous sources in Wagner who said Prigozhin was dead. But there has been no official confirmation.