Updated 10/07/15 – 2:50 p.m.

CHICAGO (CBS) — An extra-alarm fire ravaged a nearly century-old landmark church in Woodlawn on Wednesday, causing the roof to collapse, and sending gray water streaming out the front door hours after firefighters began dousing the heavy flames.

The Fire Department first responded to the fire at Shrine of Christ The King Sovereign Priest, 6401 S. Woodlawn Av., shortly before 6 a.m., when smoke alarms went off in the neighboring priory. Fire officials said the fire might have smoldered all night, after floor varnishing work in the choir loft.

“Realistically, whenever that fire started, it went unnoticed for a long period of time. That smoke could have traveled within the structure, where it didn’t come out until a window failed,” said Deputy Fire Commissioner John McNicholas. “Unfortunately, most of the roof collapsed into the structure. So as beautiful as the structure is, it sustained an awful lot of damage.”

The ornate limestone building, previously named St. Gelasius Church, received city landmark status in 2004.

When the first firefighters arrived at the scene, they saw fire through a couple windows of the church, and once they got inside, they found “an awful lot of fire within the church itself,” according to McNicholas.

Firefighters were pulled out of the building, and a defensive operation was set up to prevent the blaze from spreading to any neighboring buildings.

A total of about 150 firefighters and 50 pieces of fire equipment responded to the blaze.