The Portland Fire Department is investigating an apartment fire that broke out Saturday evening in the city’s West End.

Firefighters extinguished the fire at 165 Brackett St., a four-unit apartment building, but the building sustained significant rear damage, the department said. There were no injuries, but one pet dog was killed.

Eight firetrucks were on the scene about 7:15 p.m., and the fire appeared to be out. Brackett Street was closed between Pine and Spring streets while emergency crews were on the scene.

The cause of the fire was still under investigation as of 10 p.m. Saturday.