The 22-year-old Russian passed away on Thursday while staying at a Moscow hotel, according to the Russian Modern Pentathlon Federation (www.pentathlon-russia.ru).
"We did not find any signs that he had been attacked, while there were no suspicious signs," the Federation's press service stated, as cited by the R-Sport news agency.
"The athletes have finished their season and Alexander was not at a training camp. An unexpected cardiac arrest is our initial diagnosis. The autopsy and final results will be ready in one and a half to two months," a member of the Federation concluded.
Kukarin also won the Russian Cup this year and was a bronze medallist in the mixed relay at the European Championships.
(Reporting By Dmitriy Rogovitskiy; Editing by Rex Gowar)
