A mid-flight explosion that caused the crash of Russian Airbus A321 was not related to engine failure, according to an unnamed investigator that was cited in media reports.

Black box data from the Kogalymavia's Airbus A321 crashed en route from Sharm el-Sheikh to St. Petersburg, killing all 224 people on board. indicates a mid-flight explosion that was not related to engine failure, France 2 television reported Friday, citing an unnamed investigator.

"An explosion sound which took place during the flight can be heard on the black box recordings," the channel quotes its source as saying. According to the investigator, "the noise was not caused by engine failure."

Alexander Neradko, who heads the Russian flight safety watchdog Rosaviatsia, said Sunday there were signs that the Airbus A321, which crashed in Egypt’s Sinai desert on Saturday, had broken up at a high altitude. Moscow did not officially confirm this, saying it was too early to draw conclusions before the official investigation was over.

UK and US officials said earlier in the day there was a possibility that the crashed Russian airliner could have been brought down by a bomb.

UK media reports cited British investigators who help with the inquiry into the cause of the plan crash saying their suspicion was based on intercepted communications between Islamic State-affiliated militants operating in the Sinai peninsula.

via Sputnik