Firefighters arrived at the home around 5:20 a.m. and found the one-story brick building engulfed in flames, Battalion Chief Brian Jackson said. They managed to pull one body from the house, but the rest of the victims "were too far gone," he said.
The cause of the fire and the deaths remained under investigation.
All four were pronounced dead at the scene. The names, ages and gender of all the victims have not been released, but Deputy Chief Cecil Clay said two of the victims were adults. "As they were on their fire attack and search and rescue, they found the victims," Clay said of the firefighters. "As they were continuing their attack they were finding more victims."
Police investigators still were searching through the burned-out structure in the middle-class neighborhood Monday morning, but Sgt. Gary Knight said that is routine for any fire fatality.
While the roof and outside of the home remained intact, Clay said the interior was heavily damaged.
"It doesn't look that bad on the outside, but it was extremely hot in there," Clay said. "There was a piece of metal guttering on the back that was melted, so that's at least 1,200 degrees."
Jackson said it was too early to determine how or where the blaze started or if the home had working smoke detectors.
Melvin Watkins, whose family owns the home, said he rented it about three months ago to a single man who had two children who visited him occasionally on the weekends.
A soccer goal was set up in the large backyard of the home, where Watkins said he dropped off some items at a shed there Sunday evening.
"He was watching me and waved at me," Watkins said. "That's the last connection I had with him."
The fire comes less than a week after another blaze at a southwest Oklahoma City apartment building several miles away that killed three people. Investigators have said that fire was intentionally set.