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.
Staffordshire Police has announced that the unidentified powder which has closed the A & E department in Burton, is not being seen as suspicious.
The Accident and Emergency department at Queen’s Hospital, Burton, is currently closed due to a major incident.