A firework was set off in a postbox in High Wycombe this afternoon.
Firefighters are currently at Desborough Road and say a dry powder extinguisher had to be used to put the fire out.
Royal Mail has been informed and Bucks Fire and Rescue has urged anyone with information about whoever launched the firework to call 101.
A fine of up to £5,000 can be given, along with a six-month prison sentence - for using fireworks illegally.
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