Juveniles were seen running from St John's Church moments before it caught fire, police have confirmed.
Senior Sergeant Denton Grimes of Bay of Plenty police said the fire investigator was still on the scene, determining the cause of the blaze.
He said it was yet to be confirmed as suspicious but "names of juveniles have been passed on to police".
No arrests have been made at this stage, he said.
The minister of a Rotorua church gutted by fire last night says he is "deeply saddened" by the damage but thankful no one was hurt.
At least 10 fire crews battled the blaze at St John's Church on the corner of Victoria and Ranolf Sts.
Reverend Ed Masters said the church was a pillar in the community and the congregation would be upset by its loss.
"It is a difficult time for all involved. Our focus in the coming days will be on providing support to our congregation and community, and on finding ways to continue to provide regular worship and outreach programmes. I know that in the future we will be looking to rebuild our church."
His comments echoed what a property manager at the church, Luke Martin, said last night.
It was "heartbreaking" to look at the destruction the inferno caused, Mr Martin told the Rotorua Daily Post.
"It's no good at all. There are so many lives involved in the place. Even though it is a modern church, there is a lot of history attached to it, for instance the stained glass windows that had been gifted by early settlers in Rotorua."
It's unclear what caused the blaze, but Mr Martin said everything was fine when Mr Masters locked up the building about 5pm.
The fire service was called less than an hour later, at 5.48pm, a Northern Fire Communications staff member said.
Locals Bruce Norman and his wife Phillipa were at the church this morning surveying the damage.
Mr Norman said he had played at the church on a number of occasions as he was the musical co-ordinator for the banner group Gabriel's Presence.
As a member of St Mary's Church he said he would like to see his own church open its doors to give the St John's congregation space while it worked out what it did for the future.
"It's devastating to see their loss and we as a community will support them ... it's such a shame to see one of the icons of Rotorua gone," Mr Norman said.