After a tornado devastated Picher on Saturday, many of whose residents had fled under a voluntary federal buyout scheme earlier.
Local residents said the tornado created a "surreal scene" as it moved in late in the afternoon, injuring 150 people, overturning cars, throwing mattresses and twisted metal high into the canopy of trees.
The tornado was the deadliest in Oklahoma since a May 1999 storm that killed at least 44 people in the Oklahoma City area.
The National Weather Service estimated that at least eight tornadoes had been spawned in Oklahoma along six storm tracks.
The same storm system then moved into southwest Missouri, where it claimed at least 14 more lives.
In the town of Seneca, near the Oklahoma border, crews on Sunday searched farm fields looking for bodies and survivors.