An investigation is underway after a man, a woman, and a dog were found dead Thursday night after a fire at a Capitol Hill apartment.

Just after 11:30 p.m. Thursday, Seattle Fire Department crews responded to reports of flames coming through a third-floor window in a building at 23rd and Madison Street in the Miller Park neighborhood.

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When crews got to the scene, the fire had burned through the window, and they say the flames started to reach toward the eaves of the roof.

Crews were able to start extinguishing the fire from the outside, and some firefighters used ladders to start assessing the extent of the fire in the roof. Once inside the building, firefighters noticed smoke billowing from behind one apartment unit’s door, but protective fire doors kept the fire contained.

A crew gained entry to the apartment, where they found furniture and other items blocking access to rooms. They moved these items into the hallway and started searching for occupants and extinguishing the fire.

Once inside, they found a man, a woman, and their dog in the living room deceased.

The fire was extinguished by 12:13 a.m.

The fire only spread through one apartment unit, but other units were damaged by water.

It’s not yet clear exactly how they died or what may have started the fire.