Firefighters responded to the blaze on the first floor of the house, on Farmers Boulevard near 111th Avenue in St. Albans, around 12:15 a.m.
Officials said the victims — squatters, according to sources, who were not identified at this time — were pronounced dead at the scene.
The medical examiner is working to determine the exact causes of death.
Four firefighters who suffered minor injuries were transported to a local hospital.
The fire department got the blaze under control by 1:35 a.m.
The house was under construction or abandoned, police said.
The cause of the fire remains under investigation.