An investigation is underway into the cause of a fire at the Royal Mint in the south Wales town of Llantrisant.
The emergency services were called to tackle the Royal Mint fire
The Ministry of Defence will try to establish how the fire which broke out at 1545 GMT on Monday started.
More than 20 firefighter appliances were called to tackle the blaze which was confined to one building at the 38-acre complex.
Early indications suggest the fire may have started in electrical equipment. No one was injured in the incident.
Residents living near the site were urged to keep windows and doors shut and remain indoors during the fire due to the presence of chemicals at the site which could cause irritation to eyes, nose and throat.
Following the blaze, South Wales Fire Service said no toxic substances had contaminated any water courses within the area.
The fire was reported at 1545 GMT on Monday and took more than two hours to bring under control.
The Royal Mint said its staff had been safely evacuated from the area affected.
"The Royal Mint places the highest importance on the safety of its personnel and has stringent health and safety procedures in place," it said.
"It is too early to identify the cause of the fire."
The first phase of the Royal Mint was opened by the Queen at Llantrisant, 10 miles west of Cardiff, in 1968.
It supplies coins and coinage blanks to about 100 countries, as well as making products such as military, civilian and commemorative medals.