Authorities said they had launched a probe into the cause of the blaze that destroyed the Security Directorate building in the city 110 kilometers (70 miles) northeast of Cairo.
Several people could be seen trapped inside the burning building, screaming for help from the windows, in video footage shared on social media, and emergency crews were later seen deploying a crane to rescue them.
No fatalities have been reported from the at least eight-storey tall building that was fully staffed with police when it was engulfed by flames overnight.
Fifty ambulances rushed to the scene, joined by two army planes and military emergency services, according to the health ministry and local media.
Crowds of onlookers flocked to the base of the building as the flames raged through it, sending black smoke billowing into the night sky.
Twelve people were treated at the scene, the health ministry said, and 33 more were taken to hospitals in Ismailia and nearby Suez, according to the public prosecutor’s office.
Most suffered burns or smoke inhalation in the fire, first reports of which were received at 4:30 am (0130 GMT).
By dawn, the building had been reduced to a blackened concrete shell as emergency services hosed it with water to prevent the blaze from flaring up again.
Authorities have not said how many police or detainees were inside the building, and security forces later sealed off the area, AFP correspondents reported.
Deadly blazes
Interior Minister Mahmoud Tawfik ordered an investigation into the cause of the fire and a “structural safety review” for the building, his ministry said.
On social media, Egyptians demanded information and accountability.
Deadly fires are a common hazard in the north African country where fire codes are rarely enforced and emergency services are often slow to arrive.
In August 2022, a fire blamed on a short circuit killed 41 worshippers in a Cairo Coptic church, prompting calls to improve infrastructure and response times.
Most suffocated while trying to flee the building, and others jumped out of windows to escape the blaze, as firefighters took over an hour to arrive through a maze of alleyways.
Monday’s fire in Ismailia raged through one of dozens of new police headquarters that have been built or renovated across the country over the past decade.
In March 2021, at least 20 people died in a fire at a textile factory in the capital, after two hospital fires killed 14 people the previous year.