Newly released documents show 500 out of an estimated 7000 border and managed isolation staff were tested for Covid-19 in the first week of August.
Five days later, the first Covid-19 cases in the new Auckland cluster were reported.
The government documents give a weekly summary of border work, following a Cabinet minute in July about testing border workers.
In a briefing on 7 August, 211 out of 5000 border staff at Auckland airport had been tested in the previous week.
There was a "plan in place for Wellington and Christchurch to commence testing week commencing 10 August." The first new cases were reported on 11 August.
For staff at border accommodation, it said: "Work is underway to commence weekly testing of asymptomatic workers in quarantine facilities and a rolling schedule of fortnightly testing for workers in managed isolation facilities."
Similar figures were in the previous weekly updates.
It is not clear whether ministers saw the documents although one was attached to a Cabinet paper in July.
The day before the new cases, Cabinet signed off on changes to the maritime border plan requiring port workers and ship crew leaving their vessel to wear PPE and socially distance.
Ministers directed Health and Customs officials to "work together to strengthen the testing regime that applies to port workers".
Two tests were carried out at maritime ports in the week ending 6 August, out of an estimated border staff of 2100 people.
"Testing at Port Taranaki and Port of Lyttleton commenced this week, with testing at the Port of Auckland to commence next week. This week's priority has been given to consulting with the port staff, highlighting the need for testing, requirements and procedures. All other DHBs with port facilities are developing their plans for rolling out testing of maritime border workers, with testing expected to begin over the next few weeks."
Bringing in film crew
Other documents released today show ministers may not have had the powers to allow Hollywood film crews into the country during the first Covid lockdown.
By June, officials had received legal advice that all approvals for essential workers since April needed to be re-made because a Cabinet decision did not appear in immigration instructions.
That Cabinet decision had also defined exemptions for essential workers as being overseas workers critical to the Covid-19 response or maintaining infrastructure.
Officials were concerned whether film casts and crews were starting to widen that definition.
They also said border exemptions opened the door to legal challenges from rejected businesses which offered the country similar economic benefits.
"The key judicial review risk lies not in approved applications, but in declined applications that may appear to be similar to approved ones in terms of economic significance," said a May briefing.
"While there is a risk that decisions under your delegation that extend beyond the essential services (as defined in Alert Level 4) could be ruled ultra-vires, a reasonable argument can be made that these decisions may fall within your delegation. Based on the Cabinet decisions we consider it is not entirely clear."
It pointed to work being done to expand the exemptions.