TimesLIVE reported earlier that the alleged rapist, who lived in the same street as the four girls, lured them to his house by promising to buy them chips and sweets.
Police spokesperson Cpt Andre Beetge said the alarm was raised after an 11-year-old girl was admitted to Dora Nginza Hospital on June 24. She was bleeding from her private parts.
The girl told the doctor who examined her, two days later, that she had been raped.
He said she had also mentioned the man's name and another victim. Shortly afterwards three more girls had come forward to open cases against the suspect.
Beetge said a nine-year-old girl opened a rape case, a second nine-year-old girl opened a sexual assault case while a 12-year-old girl opened an attempted rape case.
The incidents happened between 2017 and 2018.
The man was arrested and charged with two cases of rape, one attempted rape case and a sexual assault case.
Motherwell cluster commander Maj-Gen Dawie Rabie said the children seemed to have fallen prey to a serial rapist.
"We urge parents in this area to come forward where more child victims are identified. We also need parents to see the serious need of better adult supervision when children are allowed to play outside in the streets."