Blaze that gutted Port Kembla building being treated as suspicious

Officers from Lake Illawarra Police District have established a crime scene on Military Road and detectives have visited the site.

An investigation into the circumstances of the fire is now underway and police urge anyone with information to call Crime Stoppers on 1800 333 000.

Fire and Rescue NSW was called to the scene about 2am after receiving numerous triple-0 calls reporting the blaze, which took hold in a two-storey building with a basement level.

"The top two levels were fully involved when we arrived," FRNSW Warrawong Station Officer Mick Adams said.

The ladder platform was called in from Wollongong to allow firefighters to attack the fire on the top level.

Station Officer Adams said firefighters faced an additional hazard because live power lines running from the building across Fitzwilliam Street had caught alight.

But Endeavour Energy attended and cut the lines down, he said, giving firefighters better access to fight the blaze.

It took firefighters two hours to extinguish the fire.

Station Officer Adams said firefighters were unable to determine its cause due to the extent of the fire.

Police investigators and FRNSW investigators are expected to attend the scene later on Wednesday.

The building was a commercial premises which was understood to have housed a recruitment agency and an electric vehicle business.

Firefighters from FRNSW stations in Warrawong, Wollongong, Dapto, Unanderra and Shellharbour fought the fire.