Firefighters were sent scrambling across the suburb following multiple triple-0 calls alerting them to different fires at 7.50pm on Monday, April 15.

"We got a lot of calls because of where it was, there were calls for multiple locations," Fire and Rescue NSW Inspector Andrew Erlik said.

The blaze was located in a work site building that is part of the $390 million Mount Ousley Interchange project.

It took around 10 minutes for FRNSW crews from Wollongong, Balgownie and Corrimal to bring the blaze under control.

"There's not much left, other than metal," Insp Erlik said.

The work site building is located near the cleared section of trees on the M1 at West Wollongong.

Police and fire investigators were called to the scene and the cause is being treated as suspicious.

If you have any information call Crime Stoppers on 1800 333 000.