Kenyan former world 800 metres bronze medallist Kipyegon Bett died on Sunday from kidney and liver failure at the age of 26, his family said.
Bett was one of Kenya's most promising middle distance runners but was banned by the World Athletics Integrity Unit (AIU) in August 2018 for four years after he tested positive for the performance- enhancing substance erythropoietin (EPO).
Kirui said Bett had been taken into hospital in his home town of Kericho in western Kenya a week before his death.
He was later discharged but then readmitted on Friday after his condition worsened.
"He had been having problems with his kidneys," Kirui said.
"But later the doctors realised that his liver was failing as well and they prescribed some drugs for him on the first visit to the hospital, only for the doctors to discover that both of his organs had failed before he passed on Sunday morning at 11 am."
Bett won the world Under-20 800m title in Bydgoszcz , Poland in 2016 and took the bronze medal at the 2017 World championships in London.
He had also demonstrated his prowess earlier in 2017 when he powered to victory in the Shanghai Diamond League meet, eclipsing a strong field that included compatriot David Rudisha, the 2012 Olympic gold medallist and world record holder, who finished fourth.
Numerous doping scandals have tarnished Kenya's reputation as a track and field powerhouse.
About 80 athletes from the East African nation have been sanctioned in the last three years alone.