Madison Fire Department determined Tuesday that an unattended burning candle was the cause of a fire at Sigma Phi Fraternity last Friday. The unattended candle ignited a fabric cover that was draped over a podium located in a secret room, and the fire also spread to a nearby sofa chair.

The fire, which caused approximately $15,000 in damage, was in a hidden room connected to the basement. The residents evacuated the building before fire crews arrived and no one was injured.

Initially, crews were unable to locate the source of the smoke when they responded at approximately 6 a.m. Friday morning, so a water stream was directed down a vent.

After extensive searching and interviews with residents, crews discovered a secret room in the basement area, unknown to fire crews but used by residents. The door to the stairwell that led to the room was made to appear as though it was part of the basement wall.

After gaining access to the room, crews were able to quickly extinguish a chair still smoldering after the water was directed down the vent from outside.

The Wisconsin State Journal reported fire department spokesman Jon Frank said the residents hampered the investigation. The room does not meet any kind of code related to its current use and the fire department told Sigma Phi that they can no longer use the room, reported the State Journal.

According to the fire department, residents described the hidden room as their chapter room. The room itself is located underground, a level below the primary basement area and has no direct access to the outside. The room contained various candles and a podium-like structure, surrounded by church-style pews for seating.

Sigma Phi house president Rob Johnson declined to comment on the fire.

It’s not clear if the fire department will seek charges against the members of Sigma Phi.

Also known as the Bradley House, the building is located at 106 N. Prospect Ave. in the University Heights Neighborhood. The building was designed by architect Louis Sullivan and was sold to the fraternity by the Bradley family. After a disastrous fire in 1972, the house was rebuilt in 1976 and named a National Historic Landmark.