This follows a sting operation conducted by the South African Border Management Authority (BMA) and the police at the Beitbridge border post on Saturday night.
BMA commissioner Michael Masiapato said over 40 buses conveying the children were stopped at the North Gate of the busy border post with Zimbabwe before they entered South Africa.
He said although the children had passports, they were travelling without parents, guardians and permission letters as regulations require.
The bus drivers claimed the children were going to play sport, but reports said they were sent by their Zimbabwean grandparents to their parents in South Africa.
“The children were being trafficked,” Mr Masiapato said, adding that they contacted officials in Zimbabwe and have sent the children back to that country.
He said human trafficking was becoming a serious issue and promised to continue conducting operations during the festive season.
Over a million Zimbabweans live and work in South Africa, and it is believed the children were going to join their parents for the Christmas holidays after closure of schools.
South Africa has grappled with a wave of illegal migrants entering the country through the northern border with Zimbabwe.
Source: bbc.com
