Waste collectors noticed smoke coming out the back of their garbage truck around 2pm while driving through the inner city today.
They followed the safety protocol to save the truck and put out the fire, which means offloading the rubbish.
After the rubbish was dumped onto the tram tracks at Haymarket, the blaze reignited.
The City of Sydney Council claims the likely cause of the fire was lithium batteries that were incorrectly disposed of in the general waste.
The council has reminded residents not to throw out lithium batteries in general waste as they can become “quite volatile when compressed”.
Fire and Rescue NSW’s Sinisa Bobosebic said the team was initially called to a truck fire where the rubbish inside was alight.
“We were greeted with rubbish here on the street which was on fire, a smouldering fire of rubbish,” he said.
“We attempted to put the fire out initially, which we thought we had done and left the scene, only to later find out we had to come back because there was a deep smouldering fire.
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“We pulled the pile apart and put out any smouldering embers.
“We then put the rubbish back into a bin and render the scene safe.”
He said the cause of the fire was likely something reacting with something else in the rubbish.
“Either someone has been careless or it’s just an accident where rubbish is mixed up and caused a chemical reaction,” he said.
The incident caused the closure of the L1 Central to Dulwich Hill light rail line between Haymarket and Convention. It is now running again.
Cleaners were at the scene and have since removed all the rubbish from the tracks.
Hay Street was also closed for a period of time due to the incident but has since reopened, Live Traffic Sydney said.