Evidence was found of WoFs being issued to vehicles without their being inspected.
"Compliance action is under way against the vehicle inspector and inspecting organisation. If further investigation finds criminal activity, we will refer it to police or other government agencies as appropriate.
"The Transport Agency will also be contacting around 320 vehicle owners with a current WoF from Gee J Auto Services and Tyres to let them know that their vehicle may have been incorrectly passed and advise them to attain another WoF inspection."
Yaea Wongchiu could not be reached for comment.
After problems were identified with the agency's control of WoF inspection, a review had by March led to the re-inspection of more than 30,000 vehicles to ensure their safety. The work of dozens of vehicle certifiers was investigated.
Sixty-five-year-old William Ball died 21 days after the crash of a car in which he was a passenger in January last year.
His seatbelt was frayed and failed.
The Transport Agency admitted knowing since 2011 that the Dargaville firm which had issued a warrant of fitness for the car was failing to do critical WoF checks.