President Vladimir V. Putin of Russia claimed on Thursday that the warlord Yevgeny V. Prigozhin and his associates may have brought down their private jet with hand grenades while possibly under the influence of cocaine — a new narrative from the Kremlin about the August plane crash widely seen as an assassination carried out by the Russian government.

Mr. Putin made the assertion at the end of an hourslong, televised question-and-answer session with international foreign policy experts in the Russian Black Sea resort of Sochi. Mr. Putin said that investigators had concluded there had been no “external impact” that caused the crash that killed Mr. Prigozhin, the founder of the Wagner private military company, and nine others.

But, he added, there was evidence that hand grenades had been detonated on board.

“The head of the Investigative Committee reported to me just the other day that fragments of hand grenades were found in the bodies of those killed in the plane crash,” Mr. Putin said.

Mr. Putin went on to suggest that Mr. Prigozhin and his associates may have been using alcohol or drugs, painting a picture of an intoxicated group of men who may have killed themselves with their own weapons.

Mr. Prigozhin and his two top deputies died in the Aug. 23 plane crash, just two months after the Wagner founder had led a dramatic, 24-hour rebellion against Russia’s military leadership.

“Unfortunately, no examination was carried out for the presence of alcohol or drugs in the blood of the victims,” Mr. Putin said, adding that Russian security forces had found five kilograms of cocaine in Mr. Prigozhin’s offices. “From my point of view, such an examination should have been done.”

The claims are unlikely to lift the cloud of suspicion hanging over the Kremlin in the aftermath of the plane crash, which American officials — and many Russians — believe was an assassination ordered by Mr. Putin.

Mr. Putin broached the circumstances of Mr. Prigozhin’s death without being specifically asked about them, instead raising the issue at the end of his response to a questioner who asked broadly about the future of private military companies like Wagner.

Mr. Putin began by saying it was the Russian Defense Ministry that had brought the extralegal mercenary force into the war effort in the first place, in a manner that he described as “clumsy.”

“It was caused by the requirements of the current situation on the battlefield, to put it bluntly," Mr. Putin said. “And when the Defense Ministry proposed that units from this company participate in military action, I didn’t refuse.”