There are unconfirmed reports that the NI fan who died in an accident Nice was from the Ballymena area.
French police earlier said that a Northern Ireland fan in his 20s fell about eight metres from a promenade onto rocks.
Supt Nigel Goddard, who is leading the PSNI team in France, said he was told the man’s death was an accident and not in any way disorder related.
Northern Ireland played Poland in the city on Sunday night in their first match of Euro 2016.
The accident happened in the early hours of Monday.
“I was informed this morning by my French counterparts of this tragic news,” Supt Goddard said.
“The processes are that the Foreign and Commonwealth Office will make contact with this man’s family.
“I believe it was an accident.”
Northern Ireland First Minister Arlene Foster attended Sunday’s game.
“The whole atmosphere was one of great excitement, great joy, all the Northern Ireland fans and Polish fans were having a tremendous experience, a tremendous time together,” she said
“So it is tremendously sad news to hear this morning that a young fan has lost his life. I do, of course, want to express my deepest sympathy to the family back home in Northern Ireland
“It is news that will come to them as a terrible shock. A young man going out there to have the trip of a lifetime and to be told that this has happened, it just is really shocking.”