South African police say thieves stole several hundred thousand dollars from a safe at a Johannesburg stadium where Justin Bieber and Jon Bon Jovi performed over the weekend.

South African media reported Tuesday that criminals climbed down a ladder and lowered themselves on ropes to enter a locked room where funds collected from concession stands at the concerts. The theft happened at Soccer City, a showcase stadium used during the World Cup football tournament in 2010.

Jacques Grobbelaar, head of Stadium Management SA, which operates the stadium, told eNCA television that he believes the heist occurred after 2 a.m. Monday, following Bieber's sold out concert. Bon Jovi performed on Saturday night.

Police Lt. Col. Katlego Mogale says authorities are investigating whether the theft was an inside job.