Convicted paedophile Brian Shofer was found hanging in his cell at the Lentegeur police station after an alleged suicide on Friday.
Police watchdog Ipid says it will investigate the circumstances of Shofer's death under police custody.
Schofer was arrested last week, amid fresh rape allegations and claims that he was luring young children online by posing as a tutor.
He was first jailed on indecent assault charges dating back to 1994 before he was released on parole.
He later re-offended after setting up a youth-care facility in Hanover Park and was released from prison in 2010.
Now it has emerged that Shofer was teaching at Lourier Primary School in Retreat this year.
Schofer was hired by the school's governing body, without a thorough background check, explains the Western Cape Education Department (WCED).
WCED Spokesperson Paddy Atwell says Schofer was hired despite his criminal record and lack of registration on the South African Council for Educators (SACE).
You're not allowed to teach if your not registered on SACE... that should immediately flag a problem.— Paddy Atwell, WCED Spokesperson
Atwell says the WCED will investigate the case of negligence and warn other schools to be vigilant.
Listen to the full conversation from CapeTalk's Breakfast with Kieno Kammies: