Hundreds of former students and teachers of a Sydney high school have added their names to a potential class action over toxic contaminants.

The old Camden High School was moved in 2001 after dangerous substances were discovered.

Leonie Curry, pictured with her husband, has a terminal brain tumour and is the lead plaintiff for the case.

The school was built on top of an old gasworks.

Now former students and teachers believe cases of cancer, tumours and birth defects may have been caused by exposure to the chemicals.

7.30 first reported last week that lawyers were preparing a class action against the Education Department on behalf of a group of 70 people.

Now that number has grown to 195.

Leonie Curry, 41, is the lead plaintiff for the case.

She is dying of a terminal brain tumour, and wants an investigation into whether the school is to blame.

"There are so many people that are sick and died, they've died already and there's a lot of people with brain tumours, it makes you wonder," she said.

Mrs Curry has already had one tumour removed, but doctors say another tumour is inoperable.

"The prognosis is they just don't know because it's a very rare tumour, it's a very rare position and even though it's a benign tumour they still grow and because of the position it can grow and your brain stem is where all the functions for your body are, your breathing, your heart rate, all that kind of stuff, so if it takes a function that's it," she said.

Mrs Curry approached lawyers after hearing of many former students of the school who were being diagnosed with serious illnesses.

One of her closest friends, Raelean Borg, died of breast cancer last year.

"When we discovered that I had a brain tumour and I wouldn't be around much longer either we were having a bit of a joke about how long we were going to last and then came round to how it was so bizarre that the two of us were going to be dead very soon," Mrs Curry said.

Teachers, former students alike affected

Mrs Curry set up a Facebook page and was swamped with feedback from former students who suspect the contaminants at the site made them sick.

Former teachers are also involved in the potential class action.

Art teacher Dale Hodges, 45, died in 2007 of thyroid and ovarian cancer.

Her partner Glenn Carson says she was fit, and had no family history of cancer.

"She trained hard, she worked hard, she wanted to live and she wanted to teach and it didn't happen," he said.

Art teacher Dale Hodges died in 2007 after suffering from thyroid and ovarian cancer.

Ms Hodges taught at the school for 18 years.

For much of the time she taught in a classroom directly on top of the site of the former gasworks.

She kept records of the contamination uncovered in 1996.

The records include a letter from the Environmental Protection Authority warning of high levels of contamination.

The letter was addressed to the NSW Education Department.

Some remediation work was done a year later, but the school was not moved until 2001.

Mr Carson says it should have happened sooner.

"You turn up to your workplace thinking it's safe - which is what a workplace should be - but obviously this workplace wasn't safe," he said.

"We just need answers.

"You need to be able to find out why in '96 they didn't do something more drastic than wait until '97 for a start, wait another year before they did anything at all, then wait another four years until they got the land at Cawdor."

Another family of seven siblings has also added their names to the case.

Mary Nolan says of her six brothers and sisters, two died of cancer and tumours, and three more have had repeated tumours detected and removed.

She wants the Education Department to investigate.

"The Education Department should do a thorough investigation into it yes. Absolutely," she said.

"I mean we went to a rural community to have seven children raised in a rural healthy environment.

"Our public school is absolutely the first place of safety that you would think you would get a healthy upbringing from.

"What's the point of giving children milk every day when you're going to actually have them sitting on toxic ground for six years every day that they attend there, there is just no point to it."

7.30 asked the Education Department why it took five years to close the school.

It ignored the question and instead sent this statement:

The department is open to review any new information available in relation to the former Camden High School site. However, at this time we have not received any complaints or claims. If any complaints or claims are received, the department will review the information and work with the relevant government agencies to take appropriate action.

Ms Nolan says her mother is devastated by the doubts about the school, and blames herself for sending her seven children there to study.

"To watch them die one by one when you think you gave them the best - she was watching out for food and vitamins and all of those sorts of things - to find out she's been sending them to a toxic waste dump everyday for so many years in their growth periods, it is very heartbreaking for her, she'd like somebody other than herself to take responsibility for it," she said.

Although almost 200 people have now joined the legal action - it remains just a small portion of the many students who went to the school.

Those involved acknowledge that proving the cause of their illnesses may be impossible.

Nonetheless, Glenn Carson, who is still struggling with the death of his partner, also wants an official inquiry.

"It'd be nice just to be able to find out what happened, why it happened and how it happened," he said.

"If it could've been prevented, why wasn't it prevented?"