The police surrounded the site after a man was killed and two others seriously injured in a shooting incident around 10.45 a.m. (local time).
"Three factory people were also at the site who were later rescued after the gunman was found dead around 5.00 p.m. (local time)," Australian ABC quoted Detective Inspector Mark Brett as saying.
"It is believed that the person died from a self-inflicted gunshot wound," Brett said.
Officers were yet to determine the motive of the shooter.
One man was earlier arrested at the scene for hindering the police, he said. "Two men with wounds were transferred to Liverpool Hospital."
Police said one of the men had emergency surgery, while the other had superficial wounds to the lower part of his body.
Police said they did not believe the shooting was terrorism-related.
Witnesses from nearby businesses said they heard five gunshots ring out, and one person said police "told us not to go near windows".
A man who works in the building complex where the shooting took place said he heard a loud bang, which he later realised was a gunshot.