Homes were evacuated after a major barn blaze involving gas bottles and petrol started.

Fire crews were called at about 11.50am yesterday to Hilltop Farm in Bulmer, near Sudbury.

A woman, who was riding a horse at the time about 500 yards from the fire, was airlifted to hospital after the animal was startled and threw her off. A spokeswoman for the East of England Ambulance Service said her injuries were not believed to be serious.

A spokesman for Essex County Fire and Rescue Service said: “Police were called to evacuate neighbouring homes and to deal with onlookers, as firefighters wearing breathing apparatus used one hose reel, one main jet and a ground monitor to tackle flames and to cool the cylinders. At 12.10pm one of the cylinders exploded.

“At 1.33pm, the fire was under control and the incident commander reported that crews in breathing apparatus were turning over and damping down. Efforts to cool the acetylene and oxygen cylinders continued.

“The incident was dealt with by 2.27pm. A joint police and fire service investigation will be carried out to establish the cause.

“Two appliances were sent initially but the incident commander requested the attendance of an additional two appliances and a water bowser.”

Crews reported that the barn was being used as a workshop and the blaze involved cylinders, gas bottles and a store of petrol.

Appliances from Halstead, Sible Hedingham, a water bowser from Coggeshall and two appliances from Suffolk attended.