UPDATED 4.50PM (AEDT) 28/02/2023

An exclusion zone at a Sydney industrial plant has been revoked, after firefighting crews safely removed highly-flammable gas from the vicinity of a chemical stack they feared was at risk of collapsing.

Specialist crews remained at the plant in the city’s south after a major hazardous materials incident was declared by Fire and Rescue NSW earlier on Tuesday afternoon.

The precautionary evacuation order was for all residents, workers and drivers within 800 metres of fire site in the Bayside area, between Hillsdale and Banksmeadow.

The blaze broke out at the plant just after 6am on Tuesday, with arriving crews spotting flames 50 metres above a 70-metre tall exhaust stack.

Staff had shut down the plant and were carrying out a controlled burn inside the stack to halt the flow of gas, Fire and Rescue NSW said.

Further alarm was raised later in the day when crews were called back to the tower amid concerns a cooling tower had suffered structural damage, and was at risk of collapse.

Tweet from @FRNSW

“Flames were seen pouring from a cooling tower as specialist staff undertook a controlled burn to stop the flow of gas, predominantly ethylene,” Fire and Rescue said in a statement.

“Concerns were raised about the possibility the tower could collapse.

“If it had given way, the structure would have likely fallen onto six trailers, each storing 1700 cubic metres of potentially-explosive hydrogen.”

FRNSW firefighters rigged up a tractor unit to each trailer and relocated them one by one, with the hydrogen cylinders, to a safe location.

It said the operation took just under an hour-and-a-half to complete, and the site was then declared safe.

“The earlier precautionary evacuation notice has now been withdrawn, with people able to return to homes and businesses in the area,” Fire and Rescue said in a statement at 4.40pm (AEDT).

“A small exclusion zone will be set up around the tower while the risk of collapse remains.”

Significant resources were sent to the scene earlier on Tuesday. They included local firefighters, HAZMAT crews, the Environmental Protection Authority, Safework NSW, NSW Police, paramedics and experts in structural collapse.

Drones were also used to monitor the towers’ structural integrity.

-with AAP