An apocalyptic-looking prominent orange flame with billowing smoke could be seen in the sky by residents in Punggol and Sengkang at night on March 30, 2017, which continued burning well into the early hours of the morning on March 31.

Okkk omgg the view from my living room.... pic.twitter.com/EdoC8hosG7

— FN❤ (@NfxMd) March 30, 2017

The orange glow was prominent enough to be seen from other parts of Singapore as well:

Singaporeans were naturally concerned there was a huge fire somewhere on the island:

Why is there like a big fire in punggol

— AhmadNizamAffandi (@FandyQAZ) March 30, 2017

Does anyone know if there was a fire at punggol?

— sutrina (@trinasux) March 30, 2017

Saw a super big fire going on at Punggol ? ?

— mango (@amiraxbdullah) March 30, 2017

Guys is it like a big fire in Punggol? Or am I seeing orange skies at 0640hrs???

— M. Zulfadli (@IzzulAyid) March 30, 2017

Well, it turns out, this is nothing new, but in fact, very periodic.

This photo was taken some time in September 2016 from Punggol:

And even way back in 2014:

If you have info about a fire visible from various parts of Singapore, tweet us. (Photo: Shawn at River Vista) pic.twitter.com/PQvTTkWalD

— Channel NewsAsia (@ChannelNewsAsia) August 13, 2014

Source of fire

For northeastern residents and others in the know, the orange flame originates from Pasir Gudang, an industrial refinery town in Johor Bahru just across the straits from Punggol.

It is almost a quarter the size of Singapore.

The omnipresent pungent smell, especially at night, that can resemble caramelised black soya sauce sometimes, also comes from across the straits.

And depending on the wind direction, black soot is occasionally blown over to Singapore and into people's homes.

Here are some photos taken in Punggol, courtesy of Raj Vincent, showing the extent of the fire from the refinery in JB on March 30: