Tokyo: High levels of E.coli bacteria forced Tokyo officials to cancel the swimming segment of Saturday's Paratriathlon World Cup, a test event for next year's Paralympics.
The health scare is the latest to highlight problems that could arise during next year's Games due to Tokyo's sweltering summer temperatures.
The Paratriathlon World Cup had already been scheduled to start earlier to avoid exposing athletes to high temperatures.
Water quality tests at Odaiba Marine Park found bacteria levels far exceeded accepted limits, forcing officials to drop swimming from the day's triathlon events, organisers said.
Soaring temperatures have killed dozens of people across Japan since late July, highlighting the possible health threat to athletes and fans. Next year's Paralympics will be held between July 24 and August 9.
Most varieties of E.coli are harmless or cause relatively minor diarrhoea, but more aggressive strains can cause severe stomach cramps, bloody diarrhoea and vomiting, and in some cases lead to a form of kidney failure.