Syed Shatir Asghrar of Universiti Teknologi Mara’s chemical engineering faculty, said the balloons might have been filled with hydrogen, as helium gas does not easily catch fire.

“Helium does not explode. Even if it comes into contact with fire, it just pops. But hydrogen is highly inflammable. It can cause injury,” he told FMT.

He said hydrogen gas is much cheaper than helium which may prompt some organisers to fill balloons with hydrogen.

He recalled another incident in Terengganu four years ago when participants in a public event were similarly injured. “There are many incidents with people getting injured in other parts of the world due to hydrogen-filled balloons.”

While both helium and hydrogen are lighter than air and suitable for use to fill balloons, Syed Shatir said the government must come up with guidelines for the use of these gases.

He said Putrajaya should ensure that event organisers are given clear guidelines on the use of balloons.

Sixteen people, aged from four years to the late-30s, were taken to Putrajaya Hospital for treatment after a bunch of balloons exploded while being used as props for the education ministry’s 2019 National Sports Month event.

Putrajaya Hospital Emergency and Trauma Department head Dr Khairul Nizam Hassan said none of the victims were in critical condition. “The victims suffered first and second degree burns. The injury areas vary with burns in the eye-brow, hair and hands. No one suffered total burns,” he said.

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. A discarded cigarette lighter was found at the scene.