Four adults died and another was injured in an overnight house fire in Chattanooga, Tennessee, early Sunday morning.

Emergency services received a 911 call about four people trapped inside a house fire at around 3:31 a.m. local time, according to the Chattanooga Fire Department. Upon arrival, responders began fighting heavy smoke and fire while searching the building.

Firefighters found four people — three men and a woman, between the ages of 35 and 85 — dead from the blaze.

One 35-year-old man had managed to escape through a second story window before the fire department’s arrival and was treated for smoke inhalation. His condition is unclear.

The Chattanooga Fire Department is working with police to investigate the cause of the fire.