Firefighters were called to Bishop Hall Lane in Chelmsford
One person has died and a hospital has lost mains power following an explosion at an electricity sub-station in Essex.
A university was evacuated, people advised to keep doors and windows shut against smoke and girls were kept inside a school until going home time.
Firefighters were called to Bishop Hall Lane in Chelmsford after the explosion covered the area with smoke.
Anglia Ruskin University was evacuated and Chelmsford General Hospital went to emergency power when supplies were cut.
Neil Fenwick, from Essex Fire and Rescue, said: "This is a large fire in an electrical sub-station which operates at 132 kilo-volts and supplies power to North Chelmsford.
"The fire is in a building containing electrical switching equipment and a transformer.
"This is likely to be a protracted incident and we are warning residents to keep their doors and windows closed."
A plume of smoke led to the evacuation of several buildings
A 200m exclusion zone set up by firefighters when they arrived on the scene has now been lifted but there is a protective cordon around the sub-station area.
Essex Police said: "There is nothing to suggest that there is more than one fatality or any other people injured following this fire. The identity of the deceased is yet to be confirmed.
"The following roads have been closed: Chelmer Valley Road, Rectory Lane and Valley Bridge Road.
"Parents are advised that schools in the area are aware of the situation and they should contact the school to find out the procedures in place for the collection of their children."
Sarah Packard, who works at Anglia Ruskin University, said everyone was told to leave the building.
"The fire alarms went off at lunchtime and I thought it was a drill.
"I was going out anyway so I picked up my bag and car keys and left. But then we got the message that the campus was closing because of the fire at the sub-station."
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One person died in the substation fire which began after an explosion