Newton was in fair condition, had no other internal injuries and would not need surgery, team spokesman Charlie Dayton said during a news conference outside a Charlotte hospital. It was unclear if Newton would be able to practice or play Sunday against the Buccaneers, Dayton said.
"Right now we have thought about Cam's well-being and we understand there was someone else in the other car who was injured," Dayton said. "We just hope that they're all OK."
He was expected to be released from the hospital on Wednesday after undergoing tests.
Television footage showed Newton on a stretcher being placed in an ambulance after the crash. Photos from The Charlotte Observer showed the 25-year-old smiling as an officer attended to him on the ground.
A black pickup truck that Charlotte-Mecklenburg police spokesman Robert Tufano said Newton was driving was overturned on the roadway with debris scattered all over the street. The roof was caved in and a tow truck later was hauling it away. Another car that appeared to be involved in the crash had front end damage.
Police were investigating how the crash happened on a bridge that crosses busy I-277 in the shadow of Bank of America Stadium, where the Panthers play. Dayton said he believes Newton was on his way to the stadium but wasn't certain.
The two-time Pro Bowler has 2,800 yards passing this season with 16 touchdowns and 11 interceptions. He also has rushed for 425 yards and 3 touchdowns to lead the Panthers to a 4-8-1 record.
An Atlanta native, Newton led the Auburn Tigers to a national championship in 2010.
Dayton said Newton had two transverse process fractures in his lower back, which is the same description of an injury that Dallas quarterback Tony Romo has and has been playing through it.
Dayton said Panthers owner Jerry Richardson stopped to visit Newton, but was unable to see the quarterback because he was undergoing tests. Richardson left to attend the league meetings in Dallas.
As word of the accident spread online, NFL players started sending good wishes on social media. "Praying for @CameronNewton," Oakland Raiders defensive end Justin Tuck tweeted.
Newton threw three touchdown passes in Carolina's 41-10 win over the New Orleans Saints on Sunday, his best game in nearly a month-and-a-half. He also broke a string of eight straight games with an interception.
The win put the Panthers back in the playoff hunt, one-half game behind the Atlanta Falcons and New Orleans Saints (both 5-8).
Newton was the No. 1 overall pick in the 2011 NFL draft and was the franchise's starter right away. He has only missed one game this season, the opener at Tampa Bay. Newton has one year left on his rookie contract after the Panthers picked up a $15 million option for 2015.
The Panthers have repeatedly said Newton is a guy they view as their franchise quarterback moving forward.
But it has been a rough year for Newton.
After the Panthers fell at home to the San Francisco 49ers in the NFC divisional playoffs in January, Newton had ankle surgery in March that sidelined him for all but one of the team's spring practices.
He returned for the start of the training camp, but then suffered another setback when he fractured his ribs during a preseason game against the New England Patriots.
The injuries forced Newton to miss Carolina's season opener.
He has said he's not been close to 100 per cent all season.
Newton is 23-31-1 as an NFL starter in the regular season and 0-1 in the playoffs.
Derek Anderson is the team's backup quarterback and would be first in line to replace Newton if he is unable to play Sunday against Tampa Bay (2-10). Anderson started and led Carolina to a season-opening victory against the Bucs.
AP Sports Writer Steve Reed and Associated Press Writer Mitch Weiss contributed to this report.