Firefighters from two departments battled a large apartment fire Thursday at 4848 N. Lydell Ave. in Glendale, where flames spread from exterior balconies into the attic and damaged units on multiple upper floors. The blaze was brought under control in about 50 minutes, after crews arrived within minutes of the first 911 calls.

The building sits on the Milwaukee-Glendale line just north of Estabrook Park, and that location sent both North Shore Fire Department and Milwaukee Fire Department crews racing to the scene. North Shore crews were dispatched at 4:40 p.m. after a 911 call reported fire in the building, Milwaukee received a simultaneous call at 4:41 p.m., and both departments arrived at 4:45 and 4:46 p.m.

About 70 firefighters responded, along with roughly 12 engine companies, eight ladder companies, a heavy rescue unit, multiple paramedic units and multiple chief officers. The fire was serious enough to draw the equivalent of a third alarm, and by the time crews got inside it was burning on balconies on the second, third and fourth floors and pushing into the attic space. Fire Chief Aaron Lipski said the fire appears to have started on one of the building's exterior porches, while Robert Whittaker said crews believe it started on a balcony and have not yet determined the cause.

The attic made the job harder. Whittaker said once fire gets in an attic, it can move fast and spread quickly, which forced crews to move hard to keep it from running deeper into the building. A fourth-floor unit sustained fire damage, some damage occurred on the third floor, and at least one apartment on the upper floors was hit hard. The fire did not spread beyond the affected apartments on that side of the building.

The sprinkler system also did not give crews an easy break. The building has sprinklers in the hallways and exit ways, but they did not activate because the heat in those areas was not enough to trigger them. Whittaker said the system worked as designed, even though it did not go off where the fire was burning.

One firefighter was evaluated for a minor injury and returned to work. One building occupant asked a paramedic to check them for smoke inhalation but refused hospital transport. Investigators do not believe the fire was suspicious and are treating it as accidental, but they still have not determined what sparked the blaze on the balcony. For now, that is the part of the fire that remains unanswered.