Police and Fire remain at the scene of a large fire at a Henderson plastic factory overnight.

"We are continuing to work with the Fire Service to assess whether the blaze was suspicious," says Detective Sergeant Ashley Matthews.

Enquiries are ongoing but at this stage the building is too unsafe to enter for further investigation and will need to be secured before Police and Fire can investigate fully.

This is not likely to be done for some time and may involve the use of machinery to make the building safe.

We are unlikely to be able to say for certain whether it is suspicious or not for several days yet.

Source: New Zealand Police.