The NZ Transport Agency is urging truck, trailer, bus, motorhome and coach owners who used the now-suspended heavy vehicle certifier Richard "Dick" Joyce to get their towing connections checked.
Close to 480 vehicles are potentially impacted, NZTA said this afternoon.
Joyce, who is being investigated by NZTA, did not wish to comment when contacted by the Herald and said he had only just received the safety alert himself.
NZTA said that as a result of its safety audits it indefinitely suspended Joyce's heavy vehicle specialist certifier appointment in June.
NZTA operational standards manager Craig Basher said it then began investigating certifications the Porirua man had carried out.
"Through that investigation we have established that there are further potential safety issues with towing connections certified by Mr Joyce which must be addressed," Basher said.
"The safety alert we have issued today requires the operators of all vehicles with potentially affected towbars, drawbeams or drawbars to urgently have them cleaned and inspected for signs of cracks or other failures, carry out daily inspections before use and discontinue using the vehicles if any cracks or failures are found."
The Transport Agency may revoke towing connections certified by Joyce in response to its investigation.