Bright orange glow spotted from Yishun to Toa Payoh: Here’s what it really was

Photos and videos of the phenomenon were also shared on social media, including in the Facebook group Cloudspotting & Skyspotting in Singapore.

Some netizens joked that the sky looked “like it’s on fire”, while others wondered if it was a large blaze.

But there was no need to panic.

The orange glow actually came from flaring activities at refineries and petrochemical plants in Pasir Gudang, Johor, an industrial town across the Straits of Johor from Punggol.

Flaring is a common safety process carried out during routine maintenance at refineries to prevent the buildup of gases. These gases are burned off, producing flames that can sometimes be seen from Singapore.

According to experts, the process mainly releases carbon dioxide and water vapour and does not pose any health risk.

Depending on wind direction, however, black soot from Pasir Gudang may occasionally drift over to Singapore and settle in homes.