A North Wollongong apartment complex has been damaged in a mysterious explosion overnight.
Residents of a complex on Virginia Street were woken about 2am Monday by a loud explosion coming from the upstairs stairwell.
The blast took out multiple windows, causing glass to rain onto neighbouring apartments.
The explosion also disturbed the stairwell’s vermiculite ceiling.
A Hazardous Materials crew sprayed down the crumbling ceiling Monday morning, out of asbestos concerns.
Detectives visited the site earlier on Monday and are investigating.
Residents have told the Mercury they emerged from their apartments to find the stairwell covered in dust with an overhead light swinging from its cable and black scorch marks at the foot of one apartment doorway.
Residents were earlier issued breathing masks as a precaution but have since been allowed to return to their homes.
Witnesses interviewed by the Mercury believe the blast originated from the landing between two apartments, one of them home to 26-year-old roommates, Samantha Phillips and Mitch Bell.
The blast caused their front door to crack and bow inward.
Mr Bell said he awoke to a "massive bang" that sounded like it was only a couple of metres away.
"It was almost like the bang was first, and then the glass shattering was just after," he said.
"I opened the door and the vermiculite ceiling was falling away. The light was swinging from the ceiling. The glass was all blown out. There was still stuff settling from the blast and this dark grey smoke. It was like a war zone."
"There was bits of explosive paper - like from firecrackers, the paper that's left over - but it was clear it was much bigger than just a bunger."
Miss Phillips said she had no idea why anyone would target the complex.
"It's a bit scary. I just hope it doesn't happen again."
A resident of a neighbouring unit, John Moore, also heard the explosion.
“It was massive, massive explosion about 2 o'clock this morning. I was laying in bed and I heard like a ssssssshhh-boom! My whole unit lit up white. I went, opened my front door and front the unit to my unit was just dust coming across.”