A fire at a Unanderra scrap metal yard, which took firefighters more than two hours to extinguish, is being treated as suspicious.
Emergency services were called to the Unanderra Recycling and Buyback Centre on Doyle Avenue about 9.10pm on Thursday and found a demountable office building well alight.
Fire and Rescue NSW Illawarra Duty Commander Andrew Erlik said a hazardous materials crew was brought in due to a number of gas cylinders located in the business' yard.
Inspector Erlik said the amount of recycling materials at the business meant firefighters had their work cut out for them.
The fire was extinguished by 11.30pm.
The site was handed to police to determine what sparked the blaze.
A crime scene was set up and examined by forensic officers.
Inspector Lee Ingmire, from Lake Illawarra Police District, said the fire was being treated as suspicious and was under investigation by the district's detectives.
Anyone with information has been urged to contact Lake Illawarra police station on 4232 5599 or Crime Stoppers via 1800 333 000.