Transport authorities from across the country are tracking down truck drivers caught up in an investigation that found they were improperly assessed for their licence.

Many of the drivers caught up in the probe never held a regular car licence before being allowed the wheel of heavy vehicles and were found trying to transfer their credentials in other states.

The deadly Mona Vale crash on Sydney's Northern Beaches in 2013. Credit:Tim Pascoe

It follows an investigation by Western Australian authorities in July, which led to more than 300 truck drivers having their licences suspended after they were found to have been improperly assessed at a Perth driving school.

The school, Mines West Truck Driving School, based out of Neerabup, conducted assessments for all heavy-vehicle types including multi-combination trucks, or road trains, which can tow two or more trailers at a time, carrying more than 60 tonnes.