The deadly fire that engulfed a government building in Johannesburg will now be subject to an investigation by the department of labour.

On Thursday, the department's spokesperson, Teboho Thejane, said they would launch their own probe in order to find out what might have caused the fire.

"The department of labour will leave no stone unturned and all those who are found to have flouted the law will be dealt with accordingly," Thejane said.

The fire that broke out on the floor occupied by the Gauteng health department resulted in the deaths of three firefighters and the injury of eight more people on Wednesday.

Thejane said employers were responsible for ensuring the safety of their workers, however, the department had the powers to inspect workplaces and enforce the law.

On Wednesday, infrastructure development MEC Jacob Mamabolo warned against speculation on the cause of the fire. But Mamabolo said a report by his department had confirmed that the building failed to comply with health and safety standards.

Thejane said no employer, including government, would be spared from facing legal consequences if found to be flouting occupational health and safety laws. He said while his department oversaw the inspection of workplaces and enforced labour laws, they also had to take action against themselves at some point.

"If you remember a few years ago we issued a prohibition order against ourselves at one of our Johannesburg offices. We felt we cannot subject our workers to an unsafe and unhealthy situation," he said.

In 2013, Sowetan published a series of reports on the state of buildings occupied by government departments in the Johannesburg CBD.

The Public Servants Association instituted a court case against the labour department in connection with the Johannesburg Labour Centre, housed in the Nedbank Mall building in Commissioner Street.

Two surveys reflected that employees had symptoms of "sick-building syndrome", such as headaches and allergies.