Specialized locator equipment on board the French vessel La Place detected signals from the seabed in the Mediterranean Sea, the Egyptian investigative committee said in a statement.
The director of the BEA, France's air accident investigation agency, later said it had confirmed the signals were from one of the recorders on the plane.
"The signal of a beacon from a flight recorder could be detected. ... The detection of this signal is a first step," BEA Director Remy Jouty said in a statement, according to an agency spokesman.
The Airbus A320, which had 66 people aboard, crashed in the Mediterranean on May 19 on a flight from Paris to Cairo.
Since then, authorities have been searching for wreckage and the plane's flight data and cockpit voice recorders, which could reveal evidence about what caused the crash.
Authorities hope to locate the data recorders, so a specialized vessel managed by the Deep Ocean Search company can then retrieve them. That vessel is set to join the search team within a week, the investigative committee said.
So far, search teams have found small pieces of debris, victims' remains and personal effects from the plane. They haven't found the aircraft's fuselage.
Analyst: Searchers are nearing wreckage
Detecting the beacon is a sign that searchers are closing in, CNN aviation analyst Mary Schiavo said.
"That means they're probably within one to three miles (of the black boxes)," she said. "That is the distance that these beacons can broadcast, so they are literally almost on top of them."
And it's likely, Schiavo said, that the recorders will be with the bulk of the wreckage from the plane.
"Hopefully they have finally got the right beacon, the right location, and soon we'll have answers," she said.
This isn't the first time investigators have said they detected a signal from the plane.
Last week a lead investigator in the search said airplane manufacturer Airbus had detected signals
from 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 gave investigators a more specific location to detect pings from the black boxes, state media reported.
Time is of the essence: The batteries powering the flight recorders' locator beacons are certified to emit high-pitched signals for about 30 days after they get wet.
Once they're found, the black boxes will be brought to Egypt, a civil aviation ministry official told CNN. That's standard procedure, the official said, similar to what happened in November with the recorders from Metrojet Flight 9268, which crashed in Egypt's Sinai Peninsula.
The data recorders have been fixtures on commercial flights around the world for decades
The flight data recorder gathers 25 hours of technical data from the airplane's sensors, recording several thousand distinct pieces of information. Among the details investigators could uncover: information about the plane's air speed, altitude, engine performance and wing positions.
The cockpit voice recorder captures sounds on the flight deck that can include conversations between pilots, warning alarms from the aircraft and background noise. By listening to the ambient sounds in a cockpit before a crash, experts can determine if a stall took place and the speed at which the plane was traveling.
But black boxes aren't perfect. In several cases -- such as the 1996 crash of TWA Flight 800
or the crash of American Airlines Flight 77 on September 11, 2001
-- authorities had hoped to find clues in the recorders, only to discover that the data inside had been damaged or the recordings had stopped suddenly.