Bomb likely the cause of explosion that downed Wagner leader Prigozhin's plane, US officials say

The explosion that downed a plane carrying Wagner Group leader Yevgeny Prigozhin and nine others in Russia was likely caused by a bomb, two U.S. officials told ABC News on Friday.

A senior U.S. official said the preliminary belief is that the private jet was downed by an explosion on board, potentially caused by a well-placed bomb. Another U.S official said the United States believes that a bomb was very likely the cause of the explosion.

The Kremlin vehemently denied having any involvement in the mysterious plane crash on Wednesday that presumably killed Prigozhin as well as Wagner Group co-founder Dmitry Utkin.

”There has been a lot of speculation around this crash [and] the tragic deaths of the plane's passengers, among them Yevgeny Prigozhin. Of course, the West presents all this speculation from a particular angle. All of that is sheer lies," Kremlin spokesperson Dmitry Peskov told reporters on Friday. "One should rely on facts. For now, there are not many facts, they have yet to be established in the ongoing investigative procedures."

There was no indication a surface-to-air missile was the cause of the crash, according to the U.S. Department of Defense.

"We don't have any information to indicate right now ... there was some type of surface-to-air missile that took down the plane, that we assessed that information to be inaccurate," Pentagon press secretary Brig. Gen. Pat Ryder told reporters on Thursday. "But beyond that, I'm really just not going to have any further information. What was it, something that came internal from inside the plane? Again, I don't have any additional insight to provide on that."

Prigozhin, 62, was a former close ally of Russian President Vladimir Putin. His private paramilitary organization played a key role in Putin's invasion of neighboring Ukraine before briefly launching an insurrection against the Russian military in June. Forces loyal to Prigozhin marched toward Moscow before turning back after several days.

Putin offered his first comments on the plane crash on Thursday hours after ABC News learned that the bodies of the victims were moved to the Tver Regional Bureau of Forensic Medical Examination.

"As for the aviation tragedy, first of all, I want to express my sincerest condolences to the families of all the victims," the Russian president said in a televised address, noting that Wagner Group made a "significant contribution to our common cause of fighting the neo-Nazi regime in Ukraine."

"I knew Prigozhin for a very long time, since the early 1990s. He was a man with a complex destiny, and he made serious mistakes in life," he added. "He achieved the results he needed both for himself and, when I asked him, for the common cause, as in these last months."

Russia's Investigative Committee has launched a probe into the incident, which "will be carried out in full," according to Putin.

"There is no doubt about that here,' he said. "Let's see what the investigators say in the near future. Tests -- technical and genetic tests -- are being carried out now. This takes some time."

Investigators said they are using DNA testing to identify the bodies, according to the Investigative Committee. They also recovered flight recorders from the site, according to the Russian news agency RIA.

Earlier Thursday, Putin addressed the BRICS summit of leaders meeting in Johannesburg remotely but made no mention of the crash in his remarks.

Meanwhile, in St. Petersburg -- Prigozhin’s hometown -- dozens of people have been arriving to light candles and drop flowers at a pop-up memorial.

The jet manufacturer that Prigozhin and Utkin were reportedly on has an impeccable record and Wednesday's crash was the first recorded in the History of the Embraer Legacy 600.

Elsewhere, Ukrainian President Volodymyr Zelenskyy made remarks commemorating marking Ukrainian Independence Day and handed out medals to Ukrainian solders.

Among the 10 people killed in Wednesday's plane crash were three crew members and seven passengers, according to Russian officials. The seven passengers identified on a flight list were Sergey Propustin, Evgeniy Makaryan, Aleksandr Totmin, Valeriy Chekalov, Dmitriy Utkin, Nikolay Matuseev and Yevgeny Prigozhin. The crew was identified as Cmdr. Aleksei Levshin, co-pilot Rustam Karimov and flight attendant Kristina Raspopova.

Russia's Federal Air Transport Agency said the plane was en route from Moscow to St. Petersburg on Wednesday when it went down near the village of Kuzhenkino in the Tver region, north of Moscow..

U.S. National Security Council spokesperson Adrienne Watson said in a statement on Wednesday that White House officials were watching the reports of the crash.

"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."

ABC News' Nadine El-Bawab, Will Gretsky, Mark Osborne, Ivan Pereira, Joe Simonetti and Tanya Stukalova contributed to this report.