Investigations into the conduct of teachers accused of sexually abusing pupils were at an advanced stage, the KwaZulu-Natal MEC for education said on Monday.

"We take the allegations levelled against the teachers very seriously and we believe that our investigation will be completed next week," said Ina Cronje on a visit to the school.

Last week the KwaZulu-Natal education department suspended five Durban teachers accused of sexual relationships with their pupils at Makhumbuza High School.

The MEC visited the school to assess if it was functioning properly after the sex allegations were made public last week.

About 20 pupils had reported that female pupils as young as 15 had sex with teachers in exchange for money and alcohol.

They alleged teachers were frequently having sex with female pupils in the science laboratory, and had even consumed alcohol with them.

The girls would allegedly receive R100 after sex.

The suspended teachers had since been replaced by temporary teachers.

Cronje, who arrived at the school two hours later than scheduled, addressed the media before attending a marathon meeting with the school governing body and teachers.

"I am here to assess the situation and see if the school is functioning properly. When the investigation is complete, we will weigh up the evidence and if there is strong evidence, we will charge them and start internal disciplinary actions," she said.

She stressed that teachers would be fired if found guilty.

Pupils, teachers and members of the governing body were coached before the media arrived to not divulge information that could jeopardise the investigation.

The chairperson of the school body, who did not want to give his name, was angry when journalists continued to pose questions even after he had raised concerns that revealing information to the media would affect the investigation.

"All I can say is that we are very concerned about the allegations and I do not want you to talk to pupils because they are minors," he said.

Cronje said the department would continue to provide pupils with psychological treatment.

"We are very delighted that they have reported this matter because normally pupils are reluctant to report such things," she said.