A camera used to record the weather 10 miles from Belper caught the moment of explosion. Four seconds into the video, a column of smoke appears in the middle of the picture.
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Cloud and outbreaks of rain will ease away eastwards during the morning, clearing the east coast around midday with sunny spells developing.
Police and emergency services are attending the scene.
Rebel-held east remains at risk while the pumping station supplying the western part of the city is once again in operation.