Los Angeles County coroner's spokesman Ed Winter said Smith was found dead at his Baldwin Hills home. Winter said he didn't know the circumstances or cause of death.
Police spokesman Richard French added the death does not appear to be suspicious.
The top overall pick in the 1967 draft after a sensational career at Michigan State, the 6-foot-7 Smith spent five seasons with the Baltimore Colts and two seasons each with Oakland and Houston. He won the 1971 Super Bowl with the Colts.
One of the most feared defensive ends in the game, Smith often drew two blockers, yet was effective enough to make two Pro Bowls and one All-Pro team. His best work, though, came in college, and Smith was enshrined in the College Football Hall of Fame in 1988.
"He was simply a good guy," former Michigan State teammate Robert Viney said in a statement released through the university. "His size made him an intimidating figure, but he was a real gentleman. He was a helluva player."
As an actor his most memorable role was playing Moses Hightower, the soft-spoken officer in the "Police Academy" series. He also appeared in such television series as "Good Times," "Charlie's Angels," and "Half Nelson," and was a regular in the ground-breaking Miller Lite commercials featuring retired players.
Born Charles Aaron Smith, he played in high school for his father, Willie Ray Smith, in Beaumont, Texas, before heading to Michigan State, where he was an All-American in 1966.
"'Bubba' Smith was a great Spartan," Michigan State athletic director Mark Hollis said in a statement. "As both a football player and later as an actor, 'Bubba' was a great ambassador for the University. It's only fitting that beginning this fall the Big Ten Defensive Lineman of the Year Award bears his name."
At Michigan State he played on some of the school's greatest teams and was one of its best players. Fans in East Lansing, Mich., would chant, "Kill, Bubba, Kill" during games and his No. 95 jersey was retired in 2006.
"I will shed some tears tonight because I've lost a great friend," Viney said. "He never sought the spotlight. He was a humble man. As I remember him, I recall the chants of "Kill, Bubba, Kill" from the crowd in Spartan Stadium. He will be missed."
Smith was part of two of the most famous football games ever played. In 1966, he was at Michigan State when the Spartans and Notre Dame, both undefeated, played to a 10-10 tie. Michigan State finished second behind the top-ranked Fighting Irish.
In 1969, he played for the Colts against the New York Jets in the Super Bowl. Led by Joe Namath, the Jets of the AFL upset the NFL champion Colts 16-7 in Miami.
Copyright 2011 by The Associated Press