It is lucky that nobody was seriously injured or killed after an arson attack at the old police station in Portadown, the PSNI has said.
The building was significantly damaged after it was set alight in the early hours of Saturday.
The blaze reignited later in the morning and the public have been advised to avoid the area.
Detectives have made an appeal for information.
NIFRS is dealing with the fire in Portadown (Liam McBurney/PA)
A PSNI spokesperson said: “We received a report shortly before 12.25am on Saturday morning, December 14, that our colleagues in Northern Ireland Fire & Rescue Service had turned out to a fire in the old police station on Edward Street.
“We believe that ignition was deliberate.
“The fire began on the top floor, and caused significant damage to the building.”
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The spokesperson added: “Those responsible are extremely lucky that they weren’t seriously injured, or worse, when they chose to take part in such a dangerous act.
“There are a number of residential properties nearby, and we are grateful that the fire did not spread.
“Inquiries are ongoing. We are appealing to anyone with any information or to anyone with CCTV or dash-cam footage that could assist the investigation to get in touch on 101 quoting reference number 31 of 14/12/24.
“The fire has reignited this morning, and officers are currently at the scene alongside fire service.
“We would ask the public to avoid the area where possible.”