A 25-year-old woman and a 2-year-old girl died Thursday evening in a Rochester apartment fire, officials said.

Firefighters arrived at a fourplex in the 400 block of 27th Avenue NE. around 5:45 p.m. to find smoke pouring from the building. Two upstairs occupants were rescued with ladders after being trapped by heavy flames and smoke, said Deputy Chief Steven Belau.

Neighbors told emergency workers that there might still be people inside the downstairs unit, and responders rushed to pull them out. The 25-year-old woman and little girl were removed from the apartment where the fire originated, Belau said. Resuscitation efforts on the woman failed and she died at the scene, he said. The 2-year-old was taken to a hospital, but could not be revived.

The woman’s relationship to the toddler was not immediately clear.

No firefighters were injured, and the cause of the fire remains under investigation, authorities said.

Belau called the blaze unusual for that time of day, reaching extreme temperatures before shattering a window.

Toxic fumes had built up inside the apartment, eventually leaking out through the window where upstairs residents began to smell rouble.

“It had obviously been burning for quite some time undiscovered,” Belau said. “It’s a terrible tragedy.”

Damage to the complex was extensive, and authorities will ventilate the building before fire marshals can investigate, he said.

One survivor reported a minor injury but declined treatment at the scene. The American Red Cross will provide housing and recovery assistance to five occupants displaced by the blaze. Fire officials estimate that damage will exceed $150,000.