A general view looking out over the Mediterranean Sea from the coastline of Alexandria where about 290 kilometers north, search operations are taking place to locate the wreckage of EgyptAir flight MS840 on May 21, 2016. Chris McGrath/Getty Images

Officials investigating the crash of EgyptAir Flight 804, which went down in the Mediterranean Thursday en route from Paris to Cairo, are still trying to figure out what occurred on the plane in the moments before its descent. So far, they have not ruled out deliberate sabotage or technical fault. Now, news about discussions between the pilot and air control in the minutes before the flight crashed raise questions about the integrity of the investigation.

Last week officials said there had been no distress call from the plane. But a French television station reported Sunday the pilot of the EgyptAir flight spoke to air traffic control in Egypt for several minutes just before the plane crashed. M6 television said the pilot told Cairo about smoke that had engulfed parts of the aircraft and decided to make an emergency descent to try to clear the fumes. (M6’s story quoted anonymous French aviation officials and was not confirmed by the French air accident investigation agency, the BEA.)

Although an airline spokesman said last week there had been a distress call from the Airbus 320, the statement was denied by the Egyptian military and by EgyptAir.

Meanwhile, Egypt is leading a multination effort to search for the plane’s black boxes, which include the flight data and cockpit voice recorders. It sent a robot submarine to look for the plane Sunday, Egyptian President Abdel Fattah al-Sisi said. Air crash investigation experts told Reuters search teams have about 30 days to listen for pings sent out from the devices.

“They have a submarine that can reach 3,000 meters underwater,” Sisi said in a televised speech. “It moved today in the direction of the plane crash site because we are working hard to salvage the black boxes.”

So far, ships and planes hovering over the water north of Alexandria, a city at the northern tip of Egypt, have found body parts, personal belongings and debris from the plane.

The EgyptAir plane vanished off radar screens early Thursday as it entered Egyptian airspace over the Mediterranean. The 10 crew members and 56 passengers included 30 Egyptians and 15 French nationals.

“Until now all scenarios are possible,” Sisi said. “So please, it is very important that we do not talk and say there is a specific scenario.”

A relative of a passenger who was flying aboard an EgyptAir plane that vanished from radar en route from Paris to Cairo overnight cries as family members are transported by bus to a gathering point at Cairo airport, May 19, 2016. Khaled Desouki/AFP/Getty Images