The chief of EgyptAir says Egypt has contracted two foreign companies to help locate the flight data recorders of the carrier's plane that crashed last week in the Mediterranean, killing all 66 passengers and crew on board.

Safwat Masalam said on Wednesday that a French and an Italian company will be working with Egyptian search teams to try and find the black boxes, which could give clues as to what happened in the final minutes of the flight. He didn't identify the companies.

Earlier, President Abdel-Fattah el-Sissi said a submarine would join the search.

Ships and planes from Britain, Cyprus, France, Greece and the U.S. are also participating in the search for the debris from the aircraft, including the black boxes. Some wreckage, including human remains, has already been recovered.

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