Four people appeared in the Manguzi magistrates' court on Monday in connection with the murder of two women accused of bewitching a northern KwaZulu-Natal school.
Police spokesman Captain Jabulani Mdletshe said police had conducted an "operation" that resulted in 13 people being taken into custody last week.
Last week five of those appeared in court on charges of murder and they were remanded in custody until next Wednesday.
On Friday a further four people were arrested and appeared in court on Monday.
Mdletshe said that none of the nine arrested were pupils of Manhlenga High School.
On the night of September 3, a group of youths dragged the two 60-year-old women, Mangubane Msaba Zungu and Qibile Thabitha Thusi, from the house to a local sports field.
There, they doused them with petrol and set them alight. Zungu died at the scene and Thusi later died in hospital.
Manguzi police believe this was an attempt by pupils to rid their school of evil spirits.
Mdletshe said at the time that pupils from the school started "acting strangely".
"Many of the pupils started crying for no apparent reason. Some claimed they wanted meat during their crying," he said.
They believed that an evil spirit had possessed them.
But the National Teachers Union (Natu) believes that jealousy might have been at the centre of the bewitching claims.
Shortly after the murders made headlines, Natu spokesman Allen Thompson said investigations by the union had revealed that one of the women had a granddaughter at the school.
He said the granddaughter had been the only Grade 12 pupil in her class who was passing her exams. The girl's grandmother was known to be an umthakathi.
Thompson said the girl's classmates then decided to take action against the umthakathi, whom they blamed for their failures at school.
He said Natu members, who had investigated the incident for the union, had told him that the second woman who was killed was simply visiting the umthakathi. - Sapa