Breeze said fire services were still unsure what the leak was and whether it was chemical or flammable.
"We still don't know what caused it but the smell has gone away," he said. "The challenge is that whatever it was that leaked has done its dash so we may not find anything."
Firefighters in breathing apparatus and with gas and chemical detectors were going through ProPharma and the surrounding buildings trying to find the leak.
If it is not found the building will be ventilated, locked up and checked again tomorrow.
Employees from the building have been sent home with advice on what to do if they begin to feel sick.
"All we know is that other people are not showing signs of sickness and the status two person is getting better so that just means that whatever it was isn't going to cause long-term damage," Breeze said.