A body has been found within a bale of cardboard at a Hamilton processing plant, and police believe it is not a workplace accident.

The discovery of the man's body was made by staff at OJI Fibre Solutions cardboard processing plant.

Police are investigating who the person is and how they ended up in the bale.

They say it happened this morning.

"The New Zealand Police have the site locked down at present and we are doing everything we can to help them," Oji Fibre Solutions chief executive Jon Ryder said in a statement.

"At this point in time, it would not be prudent for us to say anything further. We anticipate being able to provide further information later this week."

A post mortem will be conducted tomorrow.

Work Safe says it has been notified and is making inquiries.

The Fire Service did not attend the incident.

OJI employs around 1850 people throughout New Zealand and has manufacturing plants in Auckland, Hamilton, Levin and Christchurch.