Staffordshire Fire and Rescue Service went to an incident at Queen’s Hospital and Hobbycraft, Burton-on-Trent yesterday.
Two fire engines from Longton and one from Burton attended, after four Hobbycraft employees went to the hospital's A&E department after coming into contact with the substance.
The powder was later identified as Napthalene, which is a low risk product, and used to fumigate products shipped from abroad.
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The woman was arrested after police found the body of an elderly woman on Sunday (22 October).
Cloudy with outbreaks of rain across the region this morning but will brighten up in the afternoon, leading to sunny spells.
A cloudy, damp and breezy start to the day but will slowly brighten up as the day goes on.