High levels of E.coli bacteria forced Tokyo officials to cancel the swimming segment of Saturday’s Paratriathlon World Cup, a test event for the 2020 Paralympics.

The health scare is the latest to highlight problems that could arise during 2020’s Summer Olympic and Paralympic 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. 2020’s Olympics will be held between 24 July and 9 August.

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.