A Sanford mussel plant in Havelock and a Sealord facility in Nelson are affected.
The Ministry for Primary Industries (MPI) said the decision was based on the Chinese interpretation of World Health Organisation's Covid-19 guidance, and food safety management.
The routine audit of the factories was done in late January. MPI deputy director-general of policy and trade Julie Collins said it was normal for issues to come up as a result.
"They raised a range of concerns relating to food safety and Covid controls and we've gone back to China customs to work through in more detail what those issues are so we can resolve the issues for those companies."
She said officials were working as fast as possible with their Beijing counterparts to resolve the problems before China essentially shuts down in just days for the Lunar New Year celebrations.
New Zealand former trade commissioner to China Pat English said relations between the two countries were strong.
"The overall relationship between New Zealand [and] China is in good heart," English said.
"It's well positioned and it's continuing as we would both hope and expect."
English said a possible factor behind the move could be that other countries view New Zealand's Covid-19 management systems as being lax, due to a lack of community transmission.
"That could be part of the perception that relative to many other parts in the world, New Zealand has Covid reasonably well contained.
"And so a lot of our day-to-day activities reflect more of a normal life than a Covid one."
Collins said officials would be explaining New Zealand's Covid-19 systems to their Beijing counterparts.
"As part of those discussions, we work through New Zealand's Covid status - that we're Covid-free at the moment and we have an elimination strategy.
"That we've got a risk-based alert system where, as we go up the levels, our food companies undertake further controls." ■
Ralph Lauren reported earnings per diluted share of $1.73 on a reported basis and $1.88 on an adjusted basis, excluding restructuring-related and other net charges for the first quarter of Fiscal 2023.