Firefighters have been tackling a fire with powder after fire broke out at a Nottinghamshire industrial unit containing magnesium.
About 20 people were inside the Meridian factory on Orchard Way, in Sutton-in-Ashfield, when it started at about 12:00 GMT.
One person was taken to hospital after inhaling smoke.
An officer said crews could not use water to put the fire out, which could take hours. The cause is yet not known.