People were asked to leave their homes as fire took hold of four remote outbuildings used as car repair workshops near Manningtree.
Firefighters from Colchester, Manningtree, Clacton, Dovercourt, Frinton, Halstead and Holbrook were sent to the scene after the alarm was raised at 12.54am.
An all-terrain vehicle and water bowser were also sent to the workshops in Harwich Road, Lawford.
On arrival, crews reported four buildings – measuring about 36 metres by 28m – were involved in the fire and “well alight”.
Essex County Fire and Rescue Service said: “Due to the remote location of the buildings, the officer in charge immediately called for the support of several other fire crews to provide a vital water supply to tackle the fire.
“As a precaution, firefighters requested that two nearby houses were evacuated. The local authority is supporting this effort to ensure residents are kept a safe distance from the area.”
At 2.24am, the officer in charge reported that the incident had been divided into areas to allow fire crews to surround the building more efficiently.
By 3.10am, firefighters had managed to isolate the electricity supply and surround the building completely.
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