(Fire Chief Marc S.Bashoor/Prince George’s County Fire/EMS Department)

Prince George’s County firefighters were called to the 3000 block of Chester Grove Road at approximately 11:15 p.m., officials said. Upon arriving, they saw that the fire had spread from the first floor of the complex to the second.

When flames caused the front wall of second-floor room to collapse, firefighters evacuated and regrouped, officials said.

None of the residents were injured. Four units were badly damaged before the fire was extinguished. The effort involved a total of 50 firefighters and took approximately 45 minutes.

Officials said they have not yet confirmed the cause of the fire, but an investigation is underway.