The siblings who died after sharing a packet of instant noodles for breakfast in November last year, had been poised with Terbufos.
The results of the forensic investigation were given to the Makofane family last week.
Terbufos is a chemical compound used in insecticides and nematicides.
It is part of the chemical family of organophosphates and it is a clear, colourless to pale yellow or reddish-brown liquid which is sold commercially as granulates.
Thato Makofane (9) and her big brother, Keamoketswe Makofane (13), mysteriously died within a short period of each other on Tuesday morning, November 9 last year.
Their death certificates state that the cause of death was still under investigation.
Their mother, Matlatsi Makofane and grandmother, Winnie Makofane, claimed the children shared a packet of instant noodles before leaving for school.
Thato left first for the bus stop to wait for the school bus.
Keamoketswe stayed behind because their mother was still helping him with an assignment that he was supposed to take to school.
After Keamoketswe received his assignment back from his mother, he followed his sister to the bus stop.
Winnie Makofane said Keamoketswe came running back home after a few minutes to report that his sister had collapsed and she was rushed to the clinic at Ext 19 where she was declared dead.
During that time, the family received a distressing call from a family friend, Mantoa Motloung, who informed them that Keamoketwe had also collapsed.
He was also rushed to the clinic where he was also declared dead.
The Makofane family said at the time they did not want to speculate about whether the noodles could have contributed to their deaths until they receive postmortem results.
Both Thato and Keamoketswe were learners at Osizweni Primary School.
Keamoketswe was a Grade 7 learner and Thato was in Grade 4.
Const Busi Mthethwa, eMbalenhle Police spokesperson, said two inquest dockets were opened because of the different scenes where the children died.
The children’ mother said as the family, they have more questions than answers now.
“We hope that police will resolve this mystery and hopefully get answers to how the children consumed poison and where it came from,” said Matlatsi Makofane.
Mthethwa confirmed that the forensic results returned and the family was informed about the outcome.
Hundreds of people, including learners and teachers from Osizweni Primary School, paid their last respects to Keamoketswe and Thato on Sunday, November 14 last year.
The funeral service was held at K.I. Thwala Secondary School and the children were laid to rest in the Ext 14 cemetery in eMbalenhle.
