A fire that engulfed an industrial estate on Sydney’s Northern Beaches is being treated as suspicious as nearby residents are urged to avoid toxic smoke and fumes spewing from the charred remains.

Flames engulfed a tyre and mechanical workshop on Old Pittwater Road in Brookvale just before 7pm on Monday.

It took more than 50 firefighters and 16 fire trucks to get the blaze under control.

On Tuesday, residents were urged to stay indoors and shut any windows as thick, acrid smoke continues to billow from the building. Some said they could smell toxic fumes and worried about a possible chemical spill, a NSW Police spokesperson said.

Several cars have been damaged by the fire and falling debris, though no injuries have been reported.

It is believed there was no one inside the building when the fire broke out.

A crime scene has been established, with police suspecting the blaze was deliberately lit.

Investigators have so far been unable to enter the building and properly assess the scene.

“The fire in the industrial complex on Old Pittwater Road continues to smoulder,” Fire and Rescue NSW said in a statement about 11am on Tuesday.

“There is still some smoke which is quickly dissipating.”

The fire is expected to smoulder for the next couple of days as firefighters continue to douse the building using aerial ladder platforms.

– AAP