WorkSafeNB is investigating an incident at the Irving Oil refinery last week where some workers were exposed to acid fumes.

The incident happened last Wednesday at the refinery's sulfuric acid regeneration plant, which was shut down for maintenance.

Dino Scichilone, the assistant regional director for WorkSafeNB, said a vacuum truck was pumping water out of a concrete pit at about 3 p.m. when some workers in the area smelled some fumes.

Scichilone said the area was evacuated and 35 workers were sent to the onsite health unit.

He said three of them required first aid treatment, including oxygen.

However, none of the workers were treated in hospital.

But Scichilone said it appears some residual acid fumes escaped from the pump truck's tank.

Carolyn Van der Veen, an Irving Oil Ltd. official, said in an email that two employees in the direct vicinity of the truck "noticed some discomfort."

She said "all employees have been cleared with no adverse effects reported."

Van der Veen said "mitigation steps have been taken" to avoid another incident but it's unclear what those include.