The Kremlin said on Wednesday that the investigation into the plane crash that killed mercenary boss Yevgeny Prigozhin included the possibility that it was caused deliberately, its first explicit acknowledgement that he may have been assassinated.

“It is obvious that different versions are being considered, including the version — you know what we are talking about — let’s say, a deliberate atrocity,” Kremlin spokesman Dmitry Peskov told reporters.

“Let’s wait for the results of our Russian investigation.”

The private Embraer jet on which Prigozhin was travelling to St Petersburg from Moscow crashed north of Moscow killing all 10 people on board on August 23, including two other top Wagner figures, his four bodyguards and a crew of three.

The cause is still unclear, but villagers near the scene told Reuters they heard a bang and then saw the jet plummet to the ground.

The plane crashed exactly two months after Prigozhin took control of the southern city of Rostov in late June, the opening salvo of a mutiny that shook the foundations of President Vladimir Putin’s Russia.

Russia has informed Brazil’s aircraft investigation authority that it will not probe the crash of the Brazilian-made Embraer jet under international rules “at the moment”, the Brazilian agency told Reuters.

Asked about that report, Peskov said: “First of all, the investigation is underway, the Investigative Committee is engaged in this.”

“In this case, there can be no talk of any international aspect,” Peskov said.

The Interstate Aviation Committee, the Moscow-headquartered body that oversees civil aviation in most former Soviet republics, said in an online statement Wednesday that it was not currently investigating the crash, although the agency has an accident investigation division.

The Russian Investigative Committee to complete its review. The committee said last week that it opened a criminal case to look into possible flight safety violations, a standard procedure in Russia when there is no immediate reason to suspect foul play.

Prigozhin, 62, was buried in St. Petersburg, his hometown, in a private ceremony that was shrouded in secrecy until Tuesday evening, when his spokespeople revealed the location of his grave.