Police spokeswoman Kammie Michael says in an email that officers stopped Hairston at a license checkpoint Wednesday night. Police also charged passengers Miykael Faulcon and Carlos Sanford with marijuana possession. All three were released on $1,000 unsecured bonds.
A university spokesman told ESPN.com that the athletic department is currently investigating the situation.
"Coach Williams and (athletic director) Bubba Cunningham are aware of a situation that took place last evening with P.J. Hairston," Tar Heels sports information director Steve Kirschner told ESPN.com via email on Thursday. "We're currently looking into it to gather the facts. We will issue a statement when we have enough information to do so."
Following an impressive sophomore campaign (14.6 PPG, 1.3 SPG, 39.6 3-point field goal percentage), the 6-foot-5 Hairston considered the NBA. But he ultimately decided to return, a move that bolstered projections for a North Carolina squad that possesses the necessary pieces to compete for an ACC title in 2013-14.
On Monday, Hairston was invited to compete for a spot on the 2013 USA Basketball World University Games team. The training camp begins on June 24 in Colorado Springs, Colo.
Information from The Associated Press was used in this report.