A fire which broke out in a plant making decoy flares for airforce planes injured six workers – three seriously – and shut down the 250-acre facility for almost a week.

The "flash fire" happened on 14 September at the Kilgore Flares Company in Toone, Tennessee and severely damaged one building. Three workers were airlifted to hospital in Memphis where they are being treated for severe burns.

The cause of the explosion is not known, but the company says it is working with state and federal regulators to determine the cause. The plant was shut until 20 September when limited operations resumed.

The employees who were injured were working on the final assembly of counter measure decoy flares used to protect air force F16s from heat seeking missiles.

In a statement the company said: “The entire Kilgore family sends our prayers and well wishes to all affected by this unfortunate incident.

“We would like to extend tremendous thanks to all of the emergency responders who worked tirelessly to control the fire and provide medical treatment to the injured employees, especially the Toone and Bolivar fire departments.

The company added that it was proud of its safety record which, up until the incident, was 4.5 million man-hours worked with only one lost time injury.