A major fire, which broke out at the SP Fireworks factory in Stafford, took three hours to bring under control.

Fifty firefighters, eight engines and four specialist fire engines were called to the scene at 5.15pm last night.

One man was treated for serious burns. Another man was taken to hospital with a back injury and smoke inhalation.

Two women were treated for smoke inhalation at the scene but did not need hospital treatment.

Police have checked employee records and two people are thought to be unaccounted for. A specialist team was searching the premises this morning

A spokesman for Stafford Police said: “This morning the focus of the joint police and fire investigation will be to recover any potential evidence from the wider scene and assess the safety of the remaining structure in order to progress the search and investigation.

“This is part of the work to establish the cause and we can’t speculate about how this explosion occurred until the forensic examination is completed.”

Local roads and business have been closed while the recovery of evidence takes place.

Police have arrested a man in connection with the incident.

Supt Ian Coxhead, from Staffordshire Police, commented: “We have a great deal of sensitive and challenging work to complete in order to allow us to establish the cause of the explosion and following fire.

“We understand the unit was storing a significant volume of fireworks which appear to have been completely destroyed during the blaze last night. This makes the ongoing examination of the scene particularly challenging and we expect to be at the scene for some time. We can confirm a 53-year-old male has been arrested in connection with the incident.”

Commercial buildings, non-domestic and multi-occupancy premises in England and Wales are already forced to undertake a 'suitable and sufficient' fire risk assessment carried out under the Regulatory Reform (Fire Safety) Order 2005.

While the overwhelming majority of premises do this, if the assessment is thought to have been carried out to an insufficient extent, the Responsible Person can face an unlimited fine or up to two years in prison.