Updated 4:40 p.m.

A fire broke out in the  Zeta Beta Tau townhouse Tuesday afternoon, with firefighters on scene using the roof to gain access to the flames.

An officer on scene, who was not authorized to speak on the record, said the fire was extinguished by 3:40 p.m.

Pete Piringer, spokesman for the D.C. fire and emergency medical services department, said the “significant fire” at 605 21st Street erupted within the upper walls of the townhouse, on the second and third floors and in the attic.

Firefighters arrived on scene and put ladders up to access the smoke-filled townhouse after receiving an initial call at about 3:05 p.m. Piringer said about 50 firefighters and 12 trucks responded.

Firefighters inside the townhouse could not immediately detect where the fire was located, Piringer said, but noted heavy smoke. He said a preliminary investigation led firefighters to believe there was “burning for a while, undetected in the walls.”

It took 15 to 20 minutes for officers “to get a handle” because the fire “wasn’t outwardly visible,” Piringer said.

No students were residing in the townhouse at the time, but one occupant who moving in smelled smoke and called the department, Piringer said. Damage to the townhouse is “pretty significant.” Firefighters opened up walls, ceilings and the roof to put out the flames.

The fire shut down 21 Street between G and F streets. Piringer said investigators will examine burn patterns and use the process of elimination to identify potential fire causes.

Neighboring townhouses did not catch flames but did hold some smoke, he said. The fraternity tweeted that all of the brothers were safe.

Priya Anand contributed to this report.