Updated 11/18/2014 – 10:57 a.m.

CHICAGO (STMW) — CTA train service has been suspended between the North Side and the Loop as firefighters continue working to extinguish a fire Tuesday morning at a 124-year-old shuttered school in Lincoln Park.

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Fire companies responded to the extra-alarm fire at the former James Mulligan Public School Building, 1855-1863 N. Sheffield Ave., Fire Media Affairs said at 2:11 a.m. Crews were still chasing hot spots as of 9:30 a.m. and expected to stay at the scene most of the day, officials said

Brown Line service remained suspended between Fullerton and Merchandise Mart as of 10:40 a.m. as crews cleared ice from the tracks, according to a service alert from the CTA. Additionally, some Loop-bound Brown Line trains will operate into the 95th-bound Red Line Loop subway. Riders can use the No. 151 Sheridan, No. 22 Clark or No. 37 Sedgwick buses as alternatives between Fullerton and the Merchandise Mart.

Purple Line service is also suspended from Howard to the Loop, the CTA said.

The blaze appeared to be on the top two floors of the building, which has been under construction.

Kristina Satek said her boyfriend lives in a home directly south of the school, and she saw the flames from his third-story window.

“I was in the kitchen, and I saw, like, a burst of flame come from the window,” Satek said. “And I don’t know if that was like, maybe the window bursting out or something. We just grabbed our stuff and left.”

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She said work at the former school building has been going on for more than a year; crews have been re-sealing the windows and hand-cleaning the bricks.

“Whoever worked on it is probably pretty bummed out right now,” Satek said.

The northern side of Satek’s boyfriend’s home appeared to be covered in ice, as was most of the school building as fire crews continued to work the fire Tuesday morning.

A sign on the fence outside the school read, “Warning: Guard Dogs on Duty; Survivors Will Be Prosecuted.”

A fire department source confirmed firefighters were confronted by two Rottweilers, which were taken out of the building and handed over to animal handlers. Neither the dogs nor the firefighters they confronted were hurt, the source said.

The building, which first opened for students in September 1890, was being considered for historic landmark status in February, according to a city document. It was closed in the early 2000s and had remained vacant until the Board of Education sold it to a private developer, the document said.

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(Source: Sun-Times Media Wire © Chicago Sun-Times 2014. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)