SIX homes had to be evacuated after two tonnes of the highly explosive ammonium nitrate were found during a barn fire.

Emergency services were called to a barn fire in the small hamlet of Gummow's Shop at around 11.43am this morning.

Once there they found the barn at Tredinnick Farm was well alight with the flames fanned by high winds creating a tall plume of smoke.

At first nearby residents were warned to stay indoors but after the discovery of the highly volatile chemical people living in six home nearby were ordered to evacuate.

It is the same chemical used in fertiliser that caused the massive explosion in Beirut last August killing more than 200 people and injuring more than 6,000.

The incident commander told ITV news that because of the volatility of the material, the high winds and smoke plume it was decided to evacuate the six homes nearby.

He said: "On arrival there was a large building approximately 100m by 80 metres. It was fully engulfed in fire. Through talking with the farmer it soon became established there was approximately two tonnes of Ammonium Nitrate which in fire conditions is explosive and very volatile.

"With that in mind because of the high winds and the high smoke plume we did a quick evacuation of the area of up to six neighbouring properties that were in the area we have evacuated."

The fire was described as a "multi-agency incident" near the hamlet in the St Newlyn East area, not far from Newquay.

In a message described as 'urgent', Cornwall Fire and Rescue Service wrote on Twitter: "Urgent - Due to a multi-agency incident in mid Cornwall, we are advising all residents in the area of Gummow's Shop to keep doors and windows closed."

Fire engines from 11 stations were called to the scene, along with Devon and Cornwall Police, South Western Ambulance Service, Cornwall Council, Public Health England, Environment Agency and the Met Office.

Two crews from Newquay and one from Truro were initially sent, along with a station manager.

On arrival, however, the first firefighters at the scene sent a message calling for first four pumps, then six, and then eight, as well as for water carriers and an aerial appliance to tackle the flames from above.

The Operational Support Unit, Environmental Support Unit and Incident Command Unit were also called in.

Resources from Newquay, Truro, Perranporth, St Columb, St Dennis, Wadebridge, St Austell, Tolvaddon, Liskeard, Penzance and Launceston were called to the scene.

The fire blocked the A3076 in both directions due to the building fire between A30 Mitchell turn off and the A3058.