Cairo: Egypt's Civil Aviation Ministry said late Wednesday that investigators have extracted "valid" data from one black box of a Russian plane that crashed earlier in the week, killing all 224 people on board.

"The investigation  team has announced that the data from the flight data recorder (FDR) has been extracted and validated," the ministry said in a statement. "It will now be subject to detailed analysis by the investigators."

Russian plane 'may have been brought down by explosive', UK says

However, the ministry said that the plane's cockpit voice recorder (CVR) is partially damaged and requires a lot of work to extract data from it.

 "Consequently, no further comment on the content of the CVR can be made. "

On Saturday, the Airbus A321 plunged shortly after taking off from the popular Red Sea resort town of Sharm Al Shaikh in Sinai, killing en route to the Russian city of St Petersburg.

The cause of the crash is not known yet.

On Wednesday, Britain delayed flights from Sharm Al Shaikh, citing concerns that an "explosive device" might have caused the Russian plane's crash. There was no Egyptian official comment on the British step.

Investigators from Egypt, Russia, France and Ireland are jointly investigating the crash

Both Egypt and Russia have dismissed a claim by a Sinai radical group affiliated to the terrorist Daesh that it had brought down the plane in a rugged area in central Sinai.