Police have discovered knives and cake in a vehicle they believe fugitive William Stewart stole and then abandoned.

Stewart, 47, has been on the run after allegedly threatening a Canterbury police officer with an iron bar in February. Police said he was possibly an armed P-addict and should not be approached.

Detective Senior Sergeant John Rae said a Toyota Hilux utility vehicle Stewart is thought to have stolen was found last week on State Highway 77 at Buccleugh, 40km northwest of Ashburton. Stewart had earlier been seen driving the vehicle.

A "considerable amount of property that did not belong to the owner of the vehicle" was inside, Rae said. "Among those items were two large knives that we believe were stolen."

Police also found an orange-coloured cake inside a plastic cake tin.

Rae asked anyone who was missing knives or a cake and container to contact Ashburton or Christchurch police.NZPA