The disappearance of the Russian airliner which crashed in Sinai on Saturday was preceded by sounds in the cockpit “uncharacteristic of a standard flight”, according to Russian media.

The Interfax news agency quoted officials in Cairo as providing a first insight into audio recordings from the Airbus 321’s “black box” recorders.

They reported that after a period of routine discussions between crew members, “the recordings show sounds uncharacteristic of a standard flight precede the moment of the airliner’s disappearance”.

According to Interfax, the recordings also suggest "there was a sudden emergency situation on board which took the crew by surprise, and the pilots did not have time to send a distress signal".

Egypt: FIRST SHOTS of the crashed Russian plane in Sinai

Confusion remains over whether the crash of the plane, which broke up in mid-air and sent debris across the remote and conflict-ridden region of Egypt, was caused by an internal fault, explosive device or external action.

On Monday evening, US intelligence officials told NBC News that an American satellite picked up a strong “heat flash” in the area at the time of the crash.

According to NBC, officials said the flash was not preceded by a heat trail from below – suggesting there’s no indication the plane was struck by a missile.

“The speculation that this plane was brought down by a missile is off the table,” the official said.

US officials pointed to an explosion on the plane itself as the most likely cause, but there is no way of telling from satellite images whether it was caused by a fuel tank or possible bomb on board.

Russian passenger plane crashes in Egypt Show all 20 1 /20 Russian passenger plane crashes in Egypt Russian passenger plane crashes in Egypt Egyptian soldiers collect personal belongings of plane crash victims at the crash site of a passenger plane bound for St. Petersburg in Russia that crashed in Hassana, Egypt's Sinai Peninsula Russian passenger plane crashes in Egypt Egyptian soldiers collect personal belongings of plane crash victims at the crash site of a passenger plane bound for St. Petersburg in Russia that crashed in Hassana, Egypt's Sinai Peninsula Russian passenger plane crashes in Egypt In this Russian Emergency Situations Ministry photo, made available on Monday, Nov. 2, 2015, showing Metrojet Airbus A321-200 flight 7K9268 flight recorder on display at an undisclosed location in Egypt Russian passenger plane crashes in Egypt Mourners lay flowers at Pulkovo International Airport outside St. Petersburg. Russia on 1 November mourned its biggest ever air disaster after a passenger jet full of Russian tourists crashed in Egypt's Sinai, killing all 224 people on board. Flags were at half mast on the parliament building, in the Kremlin, and on other official buildings in honour of the victims, most of whom were from Russia's second-largest city of Saint Petersburg Russian passenger plane crashes in Egypt People pay their respects at the entrance of Pulkovo airport outside St. Petersburg, during a day of national mourning for the plane crash victims Russian passenger plane crashes in Egypt Debris from the plane crash in Egypt Russian passenger plane crashes in Egypt A piece of an engine of Russian MetroJet Airbus A321 at the site of the crash in Sinai, Russian passenger plane crashes in Egypt The crash site debris Flight 7K9268 crashed in the Sinai peninsula, in all probability killing every one of the 224 people on board AFP/Getty Russian passenger plane crashes in Egypt The crash site debris Debris lies strewn across the sand at the crash site EPA Russian passenger plane crashes in Egypt Relatives in St Petersburg Relatives react after a Russian airliner with 217 passengers and seven crew aboard crashed, as people gather at the Kogalymaviaís information desk at Pulkovo airport in St Petersburg on 31 October AP Russian passenger plane crashes in Egypt Relatives in St Petersburg A relative of a passenger of MetroJet Airbus A321 at Pulkovo II international airport in St Petersburg, Russia, 31 October 2015. EPA Russian passenger plane crashes in Egypt The plane's journey The plane's last recorded radar position above the northern Sinai peninsula Flightradar24 Russian passenger plane crashes in Egypt Where it crashed A satellite view from Google Maps of the rough area where the plane crashed, in the mountainous Hassana region of the Sinai peninsula. Google Maps Russian passenger plane crashes in Egypt The plane The Metrojet's Airbus A-321 with registration number EI-ETJ that crashed in Egypt's Sinai peninsula REUTERS/Kim Philipp Piskol Russian passenger plane crashes in Egypt The plane The crashed Airbus A321 at Domodedovo international airport, outside Moscow,, on 20 October Russian passenger plane crashes in Egypt Relatives at in St Petersburg A relative of a passenger on MetroJet Airbus A321 at Pulkovo II international airport in St Petersburg EPA Russian passenger plane crashes in Egypt Relatives at in St Petersburg Relatives of passengers of MetroJet Airbus A321 at the Crown Plaza hotel in St Petersburg EPA Russian passenger plane crashes in Egypt Bodies being repatriated An Egyptian soldier prays as emergency workers prepare to unload bodies of victims from a police helicopter to ambulances at Kabrit military airport on 31 October. AP Russian passenger plane crashes in Egypt Bodies being repatriated Ambulances line up as emergency workers unload bodies at Kabrit military airport, 20 miles north of Suez, on Saturday AP Russian passenger plane crashes in Egypt Bodies being repatriated Egyptian paramedics load the corpses of victims into a military plane at Kabrit military air base by the Suez Canal on October 31, 2015 AFP/Getty Images

Kremlin officials have not ruled out a terrorist attack on the plane, which was carrying 224 people at the time.

But speaking to BBC News, Egypt’s President Abdul Fattah al-Sisi said that Isis’s claim to have brought down the jet at 35,000ft was “propaganda”, and said the area of Sinai in question was under government forces’ “full control”.

Meanwhile, the US Embassy in Cairo has instructed its staff to avoid travel anywhere in the Sinai Peninsula as a “precautionary measure” until further notice.

On Tuesday morning, a St Petersburg official said the first nine bodies of victims in the crash have been officially identified, and their families informed.