EWN can reveal that criminals pulled off a carefully planned, sophisticated heist at the FNB Stadium.

JOHANNESBURG - Eyewitness News can reveal that criminals pulled off a carefully planned, sophisticated heist at the FNB Stadium in Soweto just hours after the Justin Bieber concert on Sunday.

They made off with the cash takings from the weekend.

FNB Stadium was on lockdown on Monday as police, forensic experts and security company officials searched for clues into the daring heist.

The suspects used ropes and chiselled away at double-thick walls into the safe room.

Using ropes, they lowered themselves through the hole down a three metre drop.

The suspects managed to make off with cash without being detected.

Stadium Management and concert promoters only became aware of the break-in on Monday morning.

Officials believe this was a carefully planned operation as those responsible chiselled away at the wall for several days.

It is still not clear how much money was taken.

Last week, Eyewitness News revealed how for just R650, a prospective security guard was able to buy a level E, D, and C grading certificate.

Several security company insiders further revealed that the practice of buying fake certification was rife.

The probe further revealed that many guards employed at high-profile events were not qualified to be there.

FNB Stadium Management's Jacques Grobbelaar said it was a real concern.

"You could have very good people and then the last 50 of 300 or 400 guards are simply just bodies. This is a concern that we continuously address."

Measures were being put in place to ensure all guards were qualified.

Part of the investigation focused on security and organisation at FNB Stadium ahead of the Bieber and Bon Jovi concerts.