Kenyan Olympic marathon champion Samuel Wanjiru died late on Sunday after jumping from the first-floor balcony of his home in the Rift Valley, police said.
Regional police chief Jaspher Ombati said Wanjiru, 24, appeared to have suffered internal injuries after the fall and was confirmed dead by doctors at a nearby hospital.
"I can confirm that Wanjiru is dead. It is not yet clear whether it was a suicide or if he jumped out of rage, or what caused him to fall to the ground," Ombati told reporters.
"He jumped from his first-floor balcony to the ground. He was bleeding from the nose and the mouth, and may have suffered internal injuries," the police chief added.
Video footage showed police looking at blood stains on the ground below the balcony of Wanjiru's house in Nyahururu, a town in the Rift Valley some 150 km (94 miles) northwest of the capital Nairobi.
"Wanjiru's death is not only a loss to his family and friends but to Kenya as a whole and the entire world athletics fraternity," Prime Minister Raila Odinga said in a statement.
"As an athletics nation, we looked forward to a sterling performance in the Olympic Games in London next year. Mr Wanjiru was one of our sure bets for gold in the upcoming contest. His death is therefore a big blow to our dreams," Odinga said.
Ombati said police were investigating a possible love triangle that could have been behind the death of Wanjiru, the first Kenyan to win Olympic marathon gold at Beijing in 2008 and a former winner of the Chicago and London marathons.
Ombati said Wanjiru's wife, Triza Njeri, had come home to find the runner in bed with another woman, locked the couple in the bedroom and ran outside.
Wanjiru then leapt from the balcony, the police chief said.
Police said Njeri and Wanjiru's female companion were assisting with the investigation.
Last December, Wanjiru was charged with threatening to kill Njeri and the illegal possession of an AK-47 assault rifle.
Njeri later withdrew her accusation of attempted murder against him in court, saying the couple had reconciled.
Wanjiru also suffered minor injuries from a car crash in January when he swerved to avoid an oncoming truck, hit a pot hole and rolled his vehicle.
The runner defied the heat of Beijing in 2008 to triumph in an Olympic record time of two hours, six minutes and 32 seconds at the games held in China.
Wanjiru moved to Japan in 2002 as a young man to attend high school after winning a cross country selection trial in Kenya.