The sharp rise in discoveries of a notorious pest in imported cars cannot be explained, according to the Ministry of Primary Industries.
Nor is there an obvious solution to the problem.
But a special working group set up last Thursday will try to find answers.
The pest is a noxious beetle called the Brown Marmorated Stink Bug, which is found in many countries but not in New Zealand.
It inserts its fangs into fruit and vegetables, and sucks out the liquid.
Toxins from its saliva can then cause the plant to rot from within.
Agricultural organisations have praised biosecurity officers for finding the bug, and have urged continued vigilance.
But the car industry has been caught in the crossfire with no obvious solution available to it.
Three ships carrying 10,000 to12,000 cars were sent back to sea because of the bug and further cars are waiting on the docks in Japan unable to be loaded.
That is because shipping companies fear they might not be able to land at their destination.
The chief executive of the Vehicle Importers Association David Vinsen said he strongly supported biosecurity in New Zealand, but this was the worst problem he had faced in 15 years in the industry.
“We have had a number of ships turned away from New Zealand, unable to discharge their cargo of vehicles, that is the immediate problem,” he said.
“The real problem is the cars that are backed up awaiting shipment from Japan.”
Mr Vinsen said the commonly used fumigant methyl bromide caused damage to cars’ upholstery and would make them almost unsaleable.
Another compound used overseas, sulpuryl flouride, was not approved for use in New Zealand.
The approval of this chemical would be among issues considered by the special working party, according to an official in the Ministry of Primary Industries.
Also under consideration would be a requirement that fumigation takes place in the country of origin.
Mr Vinsen said the three banned ships would probably go to Australia for fumigation and then return here, but a longer term solution had to be found.
He said the hold up would not have an immediate impact on the sale of new cars because of a buffer of unsold vehicles in showrooms.
But the trade in used imports operated on the “just-in-time” principle, and so any prolonged stand-off could cause shortages to appear quite quickly.