Residents around the city and beyond are scratching their heads after hearing a loud bang on Thursday night but the cause remains a mystery.

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According to The Advertiser:

About 9.20pm, MFS crews responded to reports of a “large explosion” at Hardy St, Royal Park.

However, an MFS spokesperson said responding crews found no evidence of a fire or an explosion responsible for a large bang.

Residents took to social media to report the “loudest bang in decades” heard from West Lakes, and Cheltenham, to Roxby Downs, Hindmarsh Island and Adelaide Oval.

Locals reported hearing an explosion and seeing a bright flash around 9.15pm.