11:05 PM CDT: A Minneapolis Fire Department on-scene briefing, shared publicly by Council Member Jamal Osman, confirmed the two injured firefighters suffered minor burns and heat exhaustion and are stable. The briefing said about 50-60 firefighters battled the blaze in a defensive operation, the building had a partial rear collapse, and the fire is contained.

9:42 PM CDT: An assistant Minneapolis fire chief told NCN's correspondent on scene that two firefighters were taken to the hospital with minor injuries. A fire department explorer gave the same account.

UPDATE (5:28 PM CDT) — Citizen now describes the fire as a THREE-ALARM building fire, reporting the roof has partially collapsed on one side with the collapse ongoing. NCN's correspondent on scene confirms heavy emergency lights and a collapsed roof. This remains a developing story.

UPDATE (5:11 PM CDT) — NCN's correspondent has arrived on scene. Heavy smoke was visible over the downtown Minneapolis skyline and could be smelled from blocks away as crews continued working the two-alarm fire. This remains a developing story.

UPDATE (4:40 PM CDT) — Citizen now describes the fire as a two-alarm building fire, with residents directed away from the area. Separately, a Minneapolis police PIO told NCN's correspondent by phone that he was not aware of what had happened, including the detention observed on scene. NCN's email inquiry to MPD remains pending. This remains a developing story.

UPDATE (4:25 PM CDT) — NCN's correspondent on scene reports police have detained a person near the fire as flames continue to grow. It is unconfirmed whether the detained person is connected to the fire; no charges have been announced. NCN has not independently verified the earlier report of a firefighter in distress. This remains a developing story.

Minneapolis firefighters at the E. Franklin Ave fire scene

Saed Dahir / NCN Media

MINNEAPOLIS — Firefighters are battling a fire at an abandoned building at 1433 E. Franklin Ave. in Minneapolis, according to an alert from the Citizen app flagged as developing around 4:07 p.m. CDT Sunday.

Citizen's alert reported a firefighter in distress inside the building. Live video from the scene showed heavy black smoke rising over E. Franklin Ave.

NCN has a correspondent responding to the scene. NCN has not independently verified the report of a firefighter in distress. This is a developing story and will be updated.

— National Correspondent Network