In the past hour, EgyptAir said on its Twitter account that a distress signal had been received by Egypt's military from flight MS804 (though it is unclear whether they meant an automated signal or a manual one).
Now, Egypt's military, in a statement, says no such signal was received. We'll bring you more on that as we get it.
http://www.bbc.co.uk/news/live/world-africa-36328976