The Ministry of Agriculture expects to know by the end of the week how an imported strawberry seed-growing kit bypassed quarantine procedures.
Over the weekend, MAF recalled Buzzy Strawberry Mini Grow Kits because of concerns they could introduce viral diseases to fruit crops.
The product, imported from China, consists of small packages of strawberry seeds, a clay pot and potting mix.
More than 1300 kits have been sold through The Warehouse since September.
MAF response manager Glen Neal says a colleague saw the kits on sale and alerted him.
He says it would be normal for packs like the Buzzy Strawberry Mini Grow Kits to undergo six months in quarantine.
MAF is using independent investigators to talk to the importer and MAF staff who would have dealt with the importer to establish why that did not happen.
Mr Neil says the risk of the product importing disease is very low, but it is a concern that it should have by-passed quarantine and MAF wants to ensure it doesn't happen again.
He says about 40 kits have been returned to The Warehouse for a refund as a result of the recall.
MAF is advising people whop have the kit to wrap it in a bag and put it in the rubbish.