An arson attack on a former police station in Portadown could have ended in tragedy, the PSNI said.
The building was badly damaged in the overnight incident.
Police said it was fortunate the blaze did not spread to neighbouring buildings.
Sergeant Bigger 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.
“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.”
Police said enquiries are ongoing and they are appealing for information.
Sergeant Bigger continued: “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.”