SEOUL, South Korea (AP) — At least 83 people were treated for heat-related illnesses at the World Scout Jamboree being held in South Korea, which is having one of its hottest summers in years.

The Ministry of Interior and Safety described the illnesses as “simple exhaustion” caused by overheating and said the ill participants were treated at a hospital. It wasn’t immediately clear how many were children and their ages.

The illnesses occurred during Wednesday night’s opening ceremony of the Jamboree, which brought more than 40,000 scouts to a campsite built on land reclaimed from the sea in the southwestern town of Buan. The temperature there reached 35 degrees Celsius (95 degrees Fahrenheit) on Wednesday.

The Jamboree’s organizing committee said the events will proceed as planned and was expected to announce safety measures to protect participants in the heat.

There had been concerns about holding the Jamboree in a vast, treeless area lacking refuge from the heat.

South Korea this week raised its hot weather warning to the highest “serious” level for the first time in four years as temperatures nationwide hovered between 33 to 38 degrees Celsius (91 to 100 degrees Fahrenheit).

The Safety Ministry said at least 16 people have died because of heat-related illnesses since May 20, including two on Tuesday.