The signals were emitted by the plane's emergency locator transmitter, a device that can manually or automatically activate at impact and will usually send a distress signal. The signals from the emergency locator transmitter are different from the pings emitted by the "black boxes."
Having these signals narrows down the area that the multinational search team has been focusing on -- which a few days ago was described as "about the size of Connecticut." It dramatically decreases the search area to a 5-kilometer (3.1-mile) radius, giving investigators a more specific location to detect pings from the black boxes.
The missing EgyptAir plane, which had 66 people on board, was an Airbus A320 heading from Paris to Cairo.
A French vessel, equipped with special detection equipment to locate the pings, will begin an underwater search for the wreckage "in the coming days," according to the BEA, France's accident investigation agency. That French naval vessel, La Place, departed Tuesday from Porto Vecchio toward the Egyptian coast.
Egyptian and French submersibles have been working in the area in an attempt to find the flight data and cockpit voice recorders before their transponder batteries expire.
The French may decide to send a second ship, one equipped with an underwater exploration robot and lifting mechanics that could work in the depth of the Mediterranean. Some of the search area is as deep as 10,000 feet.
The French BEA will provide technical assistance to the Egyptian authorities, which lead the investigation and the underwater search operations.
Where the search is now
EgyptAir Flight 804 was at 37,000 feet when it lost contact above the Mediterranean early on May 19, shortly before the aircraft was scheduled to exit Greek airspace and enter Egyptian airspace.
So far, some debris from the plane -- including life vests, personal belongings and parts of wreckage -- has been recovered. Small fragments of human remains have also been found, and Egyptian officials are trying to identify and match them to passengers or crew members.
The search is ongoing for the critical parts of the plane, including the fuselage, flight data and cockpit voice recorders.
"The investigators are up against the clock," said aviation analyst Justin Green. "If they don't find the black boxes in the next 30 days, the job of finding them is going to be much harder because the black boxes may no longer be sending out a sonar ping, which will help them identify it."
Signals from plane device?
The plane has three emergency locator transmitters, one of which is in the tail, where the flight data recorders are. It wasn't clear where the emergency transmitting device had been located within the plane.
The Egyptian news agency reported that Airbus sent the information to Egyptian authorities, who then relayed the information to the search and rescue units.
Airbus would not comment when asked about the signals, saying: "We are supporting the parties in charge of the investigation and we can't comment, nor do we contribute to any kind of speculation."
The signals from emergency locator transmitters can be picked up by satellite. It is not immediately clear when Airbus received these signals, but they are more commonly identified a few hours after impact -- not a few days later.