More than 5000 litres of bitumen was inside the 20,000 litre tank when it caught fire shortly after 8.30am.

Firefighters deemed the area unsafe because of the thick, dark smoke which was billowing from the tank.

They called for the evacuation of 25 staff from the workshop and neighbouring RTA office.

It is believed the fire was sparked when an RTA worker opened the tank to inspect

the bitumen but, unknown to

him, the temperature gauge was faulty.

The content of the tank was actually too hot for the tank to be safely opened and the sudden rush of oxygen ignited the kerosene contained within the bitumen.

The tank was monitored for most of the day to make sure the fire did not reignite.

The incident is under invest-igation, according to a spokeswoman for the RTA.

“The NSW Fire Brigade HAZMAT, two fire engines and an ambulance attended but no one was injured. RTA employees returned to work at 11am,”

she said.

The spokeswoman did not provide an estimated cost of the damage.