Kamila Skolimowska, a former Olympic hammer throw champion from Poland, died suddenly after collapsing in training. She was 26.
Skolimowska, who won the gold medal at the 2000 Sydney Olympics, died Wednesday in Portugal, Poland's track and field federation said Thursday.
"This is a great tragedy to us," federation director general Jan Slezak said.
Slezak said the cause of death was not immediately clear, pending an autopsy. He said Skolimowska had complained recently of "muscle problems," but would not elaborate.
Joao Cabrita, director of the Vila Real de Santo Antonio sports complex where Skolimowska was training, said the Pole felt unwell Wednesday afternoon as she prepared for weight training.
"She fainted, lost consciousness, and we called an ambulance," Cabrita told The Associated Press. "She recovered and walked with help to the ambulance, but then she felt bad again. She fell unconscious again in the ambulance."
Doctors at a nearby medical center tried for an hour to revive her, he said.
Skolimowska was in Portugal to begin training ahead of this year's World Championships in Berlin in August.
She won gold at the age of 17 when the women's hammer throw was contested for the first time at an Olympics. She failed to medal at the 2004 Athens Games or at last year's Beijing Olympics.
In recent years, Skolimowska worked for the Warsaw police, taking care of children, Slezak said.