A San Lorenzo supporter fell to his death during the team's 3-1 derby victory at home to Huracan on Sunday.
Argentina's Ole newspaper reported that 24-year-old fan Pablo Gimenez fell 50 metres to his death at the Nuevo Gasometro shortly before the end of the match.
Gimenez collided with another supporter leaving the stadium, 33-year-old Esteban Otero, who had to be taken to the Pinero Hospital in Buenos Aires but whose condition was not thought to be life-threatening. Otero's four-year-old son, who was with him at the time of the incident, was not injured.
"We are very pained," San Lorenzo coach Edgardo Bauza told a news conference after the game. "A fan has lost his life and another is in a serious condition. We cannot celebrate as we wanted to."
Reuters reported that the incident occurred despite requests from the stadium announcer to move away from dangerous positions at the stadium.
- San Lorenzo (@SanLorenzo) March 16, 2015
The club posted on Twitter: "From San Lorenzo, we send our condolences to the family of the fan who died after falling from the home stand.
"It has been called a 'fatal accident' and at the club we are following closely the developments with the other injured fan.
"President [Matias] Lammens and other San Lorenzo directors are at the Pinero Hospital, with the family of the admitted fan."
San Lorenzo won the derby thanks to goals from Leandro Romagnoli, Matias Caruzzo and a Mauro Matos penalty after Patricio Toranzo had given the visitors an early lead.