Hundreds of foreigners have been allowed through New Zealand's closed borders, including key production crew to the blockbuster Avatar sequels.

The film industry says allowing key film personnel, like producers and cast, into New Zealand would be "huge" as it could trigger thousands of jobs for Kiwis.

Economic Development Minister Phil Twyford revealed today there was a little-known category for border exemptions for foreigners deemed essential to a project of "significant economic value".

He was granted powers by Cabinet to oversee the special applications on April 21, about a month after New Zealand closed its borders to all non-citizens and residents.

The criteria applicants have to meet include having a talent that can't be met by a Kiwi, involvement in a project which is time-critical and provides "significant economic value" or wider benefit to the economy, Twyford said.

"The bar is set very high."

Twyford didn't agree the essential worker category had been kept secret, despite it never being announced by himself or the Prime Minister at her near-daily press conferences.

Exemptions had been granted to a range of different industries, including energy and water infrastructure. Twyford wouldn't be drawn on the film industry and said it would be "inappropriate" for him to comment on.

Oscar-winning producer Jon Landau announced he'd be returning to New Zealand this week so production on the Avatar sequels could resume.

On Saturday he posted a picture on Instagram of ships that will be used in the new movies with the caption: "Our #Avatar sets are ready — and we couldn't be more excited to be headed back to New Zealand next week."

Oscar-winning producer Jon Plandau announced he's coming back to New Zealand this week to resume production on Avatar. (Photo / Instagram)

Landau told RNZ they were bringing back "far fewer people" than they had last year and only those deemed "essential" to the production's filming needs.

"We feel very comfortable because of the actions of your Government and also the responsibility the people took to really curb the virus there. So we feel we're coming back to the safest place in the world possible, thanks to a team of people that we've worked with. We believe we have a very thoughtful, detailed and diligent safety plan that will keep everybody as safe as possible in these unprecedented times."

In total, about 1500 people have been allowed through the border who aren't New Zealanders. The exemptions have mostly been to family members of Kiwis or temporary visa holders, Immigration New Zealand figures show.

Twyford said everyone had to undergo quarantine or managed self-isolation, regardless of why they were granted entry.

Chief executive of the New Zealand Film Commission, Annabelle Sheehan, said conversations were underway about a longer-term strategy to open the border to key individuals.

About seven or eight international productions are already set to start this year, which would employ up to 4000 people and inject about $400 million into the economy.

Among the international productions were Avatar in Wellington and Amazon's billion-dollar Lord of the Rings series being filmed in Auckland.

With New Zealand's success in fighting Covid-19 and its continued loosening of restrictions, Sheehan said other projects were also looking to move production here.

"Certainly there's a lot of international interest. We're aware of a number of projects that we'd be keen to see come to New Zealand because international projects only need a small number of personnel to trigger thousands of jobs for New Zealanders."

Amazon's production of its billion-dollar Lord of the Rings series was put on hold during the coronavirus lockdown. (Photo / Supplied)

If every studio in the country was booked out, it would employ 6000 workers. But there were also ongoing discussions about building new stages and infrastructure to increase New Zealand's production capacity further, Sheehan said.

Queenstown, Christchurch, Rotorua and Hamilton were all centres being considered for the potential expansion, she said.

There were 47 local productions which were shut down for lockdown and some had already been able to come back online, like Shortland Street, by working within industry guidelines.

By last Tuesday, Immigration New Zealand had received 9,140 border exemption requests - 1478 were granted.

Around half of those making requests made it under the "family of a New Zealand citizen or resident" or "New Zealand based family of a temporary visa holder in New Zealand" categories.

Most of the remaining requests were made under "critical humanitarian travel", followed by the "other essential worker" and "essential health worker" categories.

INZ said requests for a border exception have been by individuals from India, followed by Australia and South Africa.

It could not provide a breakdown of professions of those granted exemptions.

Exemptions can also be granted for Samoan and Tongan citizens making essential travel.