Authorities are investigating a gas leak at a salmon processing plant in southern Tasmania that resulted in 20 people being taken to hospital.
Tassal's Strathblane facility near Dover was evacuated around 11.30am on Sunday.
Twenty people were taken to the Royal Hobart Hospital for assessment, with six remaining overnight in a stable condition.
Four patients were still receiving treatment on Monday afternoon, the health department said in a statement.
An initial assessment by the Tasmania Fire Service indicates carbon monoxide from the operation of forklifts inside the building is likely to blame.
WorkSafe Tasmania is investigating the incident and said it had "enforced notices" to prevent further exposure.
Australian Workers Union representative Robert Flanagan said it appears the forklift being used was not fit for purpose.
"We don't understand how that could've happened," he told ABC radio.
"We have been in discussions with the company (Sunday) afternoon regarding the matter, through into the evening."
Tassal said investigations by the company are underway.
"We have been given clearance from the authorities to recommence operations," a spokesman said in a statement.
The Strathblane plant is Tassal's original processing facility and has been operating since 1986.
