According to media reports, a group of suspects managed to get into a safe room at he FNB stadium with the help of ropes and chisels. They made off with the night's concert earnings.
The break-in remained undetected on Sunday. It was not until Monday morning that stadium management and concert promoters were made aware.
Police, forensic experts and security company officials are investigating the matter and have placed the stadium on lockdown.
Bieber tweeted at TMZ about the incident, saying: "It wasn't me."