Three other people were injured, two who had been on the plane and one on the ground, WSBT-TV in South Bend reported Monday.
The jet was cleared for landing at South Bend Regional Airport about 4:30 p.m. Sunday, touched down, climbed and crashed into a nearby neighborhood, hitting the houses, the report said.
Davis, 60, who led the University of Oklahoma to its fifth national championship in the 1970s, and Wesley Caves, 58, of Tulsa, Okla., were killed, investigators said.
The plane was registered to a Helena, Mont., company owned by Caves.
Two other people who had been on the plane were identified as Jim Rodgers, reported in serious condition and Christopher Evans, who was in fair condition. Diana McKeown, who apparently was in one of the buildings hit by the plane, also was listed in fair condition. All were at Memorial Hospital.
The Chicago Tribune said Caves was flying the plane and that Davis was also a pilot.
Tinker Owens, one of Davis' receivers on two national championship teams, said, "We've lost a great Sooner," The (Oklahoma City) Oklahoman reported.
Former Oklahoma Coach Barry Switzer said on Twitter Davis was "a great role" model for young people.
"He was my 1st QB & had an outstanding career," Switzer wrote.
As Oklahoma's starting quarterback, Davis led the Sooners to a 32-1-1 record in 1974 and 1975.
He was a color commentator for CBS Sports college football in the 1980s.