The Ministry of Primary Industries (MPI) says people illegally exporting infant formula are starting to get the message that they risk being prosecuted if they don't stop.
MPI and the Customs Service announced a month ago that they were taking action against illegal shipments.
Their investigations revealed a growing trade in unregulated formula shipments, mainly to China. The agencies estimate the unlawful trade has topped $150 million.
MPI food and beverage manager Glen Neal said known unregistered exporters of infant formula have been given an opportunity to either stop trading, or carry out exports lawfully.
He said the ministry has begun an information and education programme and has completed a first round of visits to some of the larger operators.
Mr Neal said there are indications these exporters are either stopping trading or taking steps to get themselves registered.
The penalty for unregistered export of animal product is up to $300,000.
Mr Neal said it's not about the safety of New Zealand infant formula, which is highly regarded, but about protecting the confidence international trading partners in New Zealand's export standards.