Dozens of firefighters attended the blaze at the Signlab business at Alberton at 9pm Monday night after reports of a smell of burning plastic coming from a business.

The blaze was already well established and nearby residents were evacuated from their home, with one treated by ambulance paramedics for minor injuries.

A wall of the business collapsed, damaging cars on Parker Street.

Port Road was closed in both directions for about four hours but has since reopened.