Paris - French rugby was in mourning on Saturday after the death of a young player during a second division friendly match on Friday night.
Louis Fajfrowski, 21, died in the changing room of his club Aurillac, the Pro D2 team announced on Twitter.
The centre was substituted in the 60th minute after a tackle in the match against Rodez.
Stunned, he got to his feet with assistance, then left the pitch and walked unaided to the changing rooms, accompanied by a doctor.
There he lost consciousness several times. Despite the arrival of the emergency services he passed away around 20:00 local time, according to La Montagne newspaper.
An official investigation has begun into the cause of death with an autopsy scheduled for Monday.
"We will find out why he died and if the tackle provoked his death," the local prosecutor's office said.
According to the prosecutor, when the player "left the pitch his condition did not appear to be alarming. He even wanted to return (to play) afterwards, but he then began to vomit".
Tributes were made to the youngster, with French rugby federation chief Bernard Laporte saying he was "devastated".
Top14 clubs including Stade Francais, Toulon and Racing 92 added their condolences.
Fajfrowski joined Aurillac in 2015 after three seasons with Montpellier Herault's youth team.