One woman is in critical condition after a small explosion occurred at an apartment in Seattle's Laurelhurst neighborhood, the Seattle Fire Department says. Seattle firefighters responded to reports of a small explosion at a residence in the 5000 Block of Mithun PL NE just before 4:30 p.m. Friday. Neighbors reported hearing the explosion and worked to extinguish the fire. When firefighters arrived, they quickly extinguished the fire and transported the woman to Harborview Medical Center in critical condition. The fire was contained to the one unit, Seattle fire says. David Cuerpo, Public Information Officer for the Seattle Fire Department, says the cause of the fire is under investigation.