The contractor NCC informed SSAB that three office employees at the construction site showed symptoms. NCC reported the incident to the Swedish Work Environment Authority on Monday.
Several others have previously been affected. They have worked, among other things, on construction machinery at various locations in the area.
On April 3, SSAB temporarily stopped work after around 20 people fell ill, seven of whom received treatment.
Observed symptoms include nausea, headaches and respiratory irritation.
On the day work was stopped, test results showed elevated levels of toxic gas in the cabins of the machines.
SSAB now says that gas measurements of the ambient air at all temporary office premises on the construction site, including SSAB's own, have not shown any elevated levels.
It was therefore concluded that it is unlikely that corresponding gases would be present at similar concentrations inside the buildings.
