4.20pm: Authorities have called off a search in waters off Thirroul after earlier reports of a boat on fire at sea.
The crew aboard Westpac Life Saver rescue helicopter Lifesaver 21 failed to find any debris in the water during an extensive search of the ocean between Wollongong and Thirroul.
Lifesavers also failed to find any sign something was wrong and there have been no further reports of anyone missing, Surf Life Saving Illawarra's Anthony Turner said.
The search has been suspended and the incident is being treated as a likely false alarm.
Westpac Life Saver said a number of boats were checked and all were OK.
"Possibly a large cargo vessel [or] tanker that has started its engines and the exhaust smoke may have been mistaken for a smaller boat on fire," it said.
3.30pm: A number of surf lifesavers and a rescue helicopter are responding to reports a boat is on fire offshore of Thirroul on Monday afternoon.
The Sydney-based Westpac Life Saver rescue helicopter, Lifesaver 21, has been tasked as part of the emergency response, along with multiple Surf Life Saving Illawarra (SLSI) assets.
Initial reports suggest a boat is on fire about 4km offshore of Thirroul.
It is understood a member of the public alerted authorities after seeing smoke out to sea.
SLSI crews - from Thirroul, Coledale and Sandon Point - are responding to the incident on jet-skis and inflatable rescue boats (IRBs).
The helicopter is expected to arrive in about 4pm, with lifesavers already searching the water.
Police are also on scene and have set up a command post at Thirroul beach.
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