The 16, including participants and visitors aged from four to the late-30s, were taken to the Putrajaya Hospital for treatment.

The balloons, which were being used as props for the event, exploded when the education ministry’s 2019 National Sports Month event was coming to an end.

Putrajaya district police chief Rosly Hasan said someone had tried to cut the string tied to a bunch of balloons with a cigarette lighter, causing the whole bunch to explode.

He said police found a cigarette lighter at the scene.

The fitness programme was launched earlier by Deputy Education Minister Teo Nie Ching, who also took part in the activities.

Putrajaya Hospital’s Emergency and Trauma Department head, Dr Khairul Nizam Hassan, said the victims suffered first and second degree burns but no one was in a critical condition.

Deputy Prime Minister Dr Wan Azizah Wan Ismail, who had attended a Children’s Day event at a school nearby, visited the victims at the hospital.