Egypt has recovered both black boxes from a Russian passenger plane that crashed in the country's Sinai peninsula on Saturday with the loss of all 224 people on board, the civil aviation minister told a news conference.

There are normally two black boxes on an aircraft, one for cockpit voice recordings and one for flight data. Egyptian authorities had earlier said they only found one.

A militant group affiliated to Islamic State in Egypt has claimed responsibility for downing of the plane, in a statement circulated by supporters on Twitter and on the Aamaq website, which acts as a semi-official news agency for Islamic State.

"The fighters of the Islamic State were able to down a Russian plane over Sinai province that was carrying over 220 Russian crusaders. They were all killed, thanks be to God," the statement circulated on Twitter said.

But Egyptian security sources earlier on Saturday said preliminary investigations suggested the plane crashed due to a technical fault.

Russia said that the militant group's claim of responsibility could not be considered accurate. And the Egyptian Prime Minister Sherif Ismail said that there were no "irregular" activities believed to be behind the crash, adding that it would be impossible to determine the cause until the black boxes were examined.

About 150 bodies, including burnt corpses, were found in a 5 km (3.1 mile) radius from the crashed aircraft, sources said. The plane fell vertically, which led to large parts of it burning, the sources added. Search and rescue team members were still gathering the remains of victims, the sources said.

Dow Jones quoted a spokesman for the prime minister as saying 15 bodies had been recovered and sent to a morgue in Cairo. There were 214 Russian passengers on board and three Ukrainians.

Dow Jones reported that the U.S. Federal Aviation Administration in March warned U.S. airlines to avoid flying over the Sinai Peninsula below 26,000 feet. Airline routes traversing the region "are at risk from potential extremist attacks involving antiaircraft weapons," the FAA said. It noted that an Egyptian military helicopter flying at lower altitudes had been downed by extremists using a missile.

Reuters reported on Saturday that the Russian plane was at 31,000 feet when it disappeared from radar screens.

Air France and German airline Lufthansa said they would temporarily stop flying over Egypt's Sinai peninsula as a "precaution" following the crash, AFP reported.

A spokeswoman for United Continental told Dow Jones said the carrier didn't "see a need to change any of our planned routings at this time," while British Airways said it was continuing flights to Sharm El Sheikh, adding that it liaised with the appropriate authorities and wouldn't operate a route unless it was safe.