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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Another wet day tomorrow with rain continuing throughout the morning.
Heavy rain gradually moves away northwards, however it will remain cloudy with further periods of rain.
Nottingham Trent University has released a statement after building cladding inspections led to the temporary relocation of some students.