Knox CFA deputy group officer Peter Shaw said the fire, which caused $400,000 damage, started in an art supplies factory in Dorset Road and spread to two factories next to it.

Crews were alerted to the fire at 6.45pm and, due to thick smoke and a rear door being blocked, it took nearly 90 minutes to control it.

One firefighter suffered a minor injury when a piece of debris flew into his eye. The contents of the art supplies factory were completely burnt and there was significant heat and fire damage to the roof.

CFA Ferntree Gully captain Russell Stork said the fire was a timely reminder for all businesses ‘‘to take a good look’’ at their safety housekeeping.

He said small business owners could often ‘‘get a bit complacent’’ and they should ensure there is ease of access for emergency services at all times.

Mr Stork also said small businesses should check power points when multiple cords were in use.