The Department of Education is facing a huge class action legal suit from more than 300 former students and staff of a high school built over an old gas works.
Nearly half of those who are launching the case have cancer.
Thirty people who attended Camden High School have died from cancer or blood disorders with their families claiming hospital staff have worked out the source.
Leonie Curry was one former pupil who lost her battle with multiple brain tumours in June this year.
Her husband, Rod, was emotional as he remembered his wife.
"I just learned so much from her,” he told 7 News.
She was 44 years old.
Mrs Curry’s family is convinced she fell ill from toxic substances found in the soil at Camden High School.
"They all remember the black sludge, dropping the smokes down the holes and letting them explode,” Mr Curry said.
"You think you send your kids off to school, they should be safe.”
He is among 320 past students and their loved ones who've signed up to a possible class action against the Education Department.
About 30 have died from cancer including Mrs Curry's close friend Raelean Borg, who was just 40 when she passed away in 2012.
The school was built on top of Camden's old gasworks and is one of more than 60 across the state - including others at Auburn, Liverpool, Manly and Woollahra.
Joe Bonura from Marsdens Law Group said there is a great possibility the group’s suspicions are correct.
"A very real possibility of the link between their attendance at the school and their illnesses,” he told 7 News.
Camden High School was shut down 15 years ago but the empty classrooms still remain.
Work is due to start next year on a retirement village once the contaminants have been removed.
The class action is expected to be lodged next year once lawyers have built a database and have gathered expert evidence.
The Education Department is refusing to comment, pending the legal proceedings.
News break – October 9