About 9am, the Maungakaramea brigade were called to a farm on Stead Rd after a barn was discovered on fire by its owner.
The barn was empty at the time and its owner initially put the fire out before firefighters arrived.
The farm gate was lifted and Fire Service investigator Michael Champtaloup said both fires were suspicious and might be linked.
Northland police spokeswoman Sarah Kennett said police believed both fires might have been lit by the same person or people. "Forensic examination of items of interest will take place over the next few days," she said.
Meanwhile, investigations are continuing into the cause of a fire on Monday evening that destroyed the headquarters of iwi radio station Tautoko FM in Mangamuka.
Mr Champtaloup has found the blaze started at the rear of the building, in or near the computer server room. Possible culprits include a server, air-conditioning unit or multibox.
However, police are also looking into the fire and want to hear from anyone who saw anything unusual in the area on Monday evening.
Call Detective Sergeant Chris Fouhy at Kaikohe police on 09 405 2960 or Crimestoppers, anonymously, on 0800 555 111.
Mr Champtaloup said the blaze showed how fast fire could spread.
When the owner of a nearby shop called 111, the blaze was still relatively small but when the first firefighters arrived from Okaihau 23 minutes later the entire building was consumed by fire. It would have been deadly to anyone inside within five minutes, he said. Tautoko FM aims to resume broadcasting from a caravan it uses for outside broadcasts. It was the second iwi radio station in New Zealand and the first in Northland.