Residents in Middleton have complained of being disturbed by a 'massive bang' last night.
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The loud noise was reported by dozens of residents in LS10 and further afield in Rothwell, at around 9.30pm.
Residents took to social media to complain of the noise and were reassured to know they weren't 'going crazy'.
Some residents believe the source was a homemade 'mortar bomb' firework, while others say they saw the sky flash up.
One resident on Facebook said: "I’m in Middleton and it shook my windows and woke my daughter up.
"A few nearby say they witnessed a firework."
Another Middleton resident said: "I saw the firework.
"It was in this area and sounded like a bomb it was that loud. I asked my mate who I was messaging at the time who was in Rothwell and he heard it too.
"It shook all the windows and left a big black smoke cloud in the sky.
"There was another shortly after but nowhere near as loud, that was a really nice pink star burst."