Three more Customs officers have contacted Newshub to back a whistleblower's claims that slack enforcement and staff shortages are adding to risks at the border.
Last night, an officer told Newshub in an anonymous interview that it's estimated only one in every 10 packages of illegal drugs are being stopped. The same officer also has concerns about the ability of Customs to gather intelligence on travellers.
Record numbers of migrants and tourists are flying into the country, but the officer says not enough is being done to scrutinise new arrivals.
"I definitely think Customs is overwhelmed and under-resourced," he says.
He says Customs is concentrating on getting travellers through the airport in a quick and convenient manner, but its main priority should be screening them for risk.
"I believe their main concern is getting people out the door, reducing complaints from the public and basically just keeping the minister happy and the Prime Minister happy."
"The general conversation, that we are overwhelmed by risk, I don't accept that we are overwhelmed," says general manager of border operations Paul Campbell.
"I think our officers are behaving professionally and they will stop risk if they see it."
One of the ways Customs assesses risk is through the Passenger Targeting Unit (PTU). The intelligence technology helps Customs interpret red flags.
The PTU takes information from airlines, including who paid for the ticket, whether they paid cash or credit and where in the world the purchase was made. A passenger's travel history can also be analysed.
But our source says only three airlines -- Air New Zealand, Qantas and Emirates -- allow Customs access to all the data they ask for.
"I think it's a massive problem," says the whistleblower. "I think if you're only getting half the picture, you're going to catch half the bad people that are out there that you're looking for."
"The reality is yes, it's a rich picture," says Mr Campbell. "Yes, it could always be richer.
"We work with a large number of airlines, and obviously we want to be able to harvest information from all airlines."
He accepts there's disquiet among staff. A recent survey we've obtained shows 31 percent feel "disengaged" in their work.
While the officers we talked to say there aren't enough staff, a restructuring of the organisation could cut even more. Mr Campbell says he doesn't "know at this point" about job losses.
Mr Campbell says the restructure will lead to a renewed focus on enforcement.
"Put more focus on risk assessment, put more focus on intelligence, put more focus on the broad career of Customs officers".
Our whistleblower is not alone in his concerns. Three other officers have now contacted Newshub to say they have concerns about staff numbers and pay.
On those claims our whistleblower made last night that Customs only intercepts 10 percent of illegal drugs arriving at the border, two of those officers say that figure's correct.