Workers from a cluster of Mayfield businesses, where a suspected chemical leak prompted two evacuations in as many days, say they have heard little about what caused the strong napthalene odour that occurred before more than a dozen people were taken to hospital on Monday.
Employees at a Woodstock Street shipping container manufacturer evacuated for about one hour on Tuesday, after a four-hour evacuation of multiple businesses in the area on Monday.
Thirteen people were taken to hospital during Monday's incident, suffering headaches, nausea and vomiting.
The Newcastle Herald understands those people have since been released from hospital and have recovered.
Tuesday's was a self-evacuation, while Monday's came under the direction of NSW Police.
The NSW Environment Protection Authority said on Wednesday it was continuing to investigate "possible sources of odours in the area".
A spokesperson said EPA officers had attended the site and were aware of the second evacuation.
"The EPA is working closely with the affected workers and surrounding businesses," he said.
The Herald spoke to workers in Woodstock Street on Wednesday, who said the smell had only become a problem this week and had not been an ongoing issue.
One man, who asked not to be named, said it had been difficult to get information from the EPA. He said no-one seemed sure where the smell originated.
"Trying to get information out of the EPA is near impossible," he said.
"I just think the authority in charge of that needs to be more open.
"I grew up when BHP was fully fledged, but that smell the other day was horrendous."
The Herald reported earlier this week that a chemical plant on Woodstock Street, which has a napthalene still on site, denied responsibility for Monday's incident - though it said it would review its operations before the evacuation.
When contacted for an update on Wednesday, Koppers Carbon Materials and Chemicals forwarded the same statement it issued at the beginning of the week.
It said Koppers was treating the incident "very seriously".
"At this stage, our initial investigations indicate that Koppers operations were normal at the time of the incident," the statement said.