A Tauranga fire investigator says a working fire alarm system has saved a historic Te Puke church from burning down.
A Northern Fire Communications spokesman said firefighters were called to a small fire in an exterior air conditioning unit at St John the Baptist Church on Jocelyn St about 3am.
Bay of Plenty Coast fire inspector Jon Rewi said a fire alarm system inside the church which had smoke detectors alerted the fire brigade of the blaze before it got out of hand.
"That saved the inside of the church," Rewi said.
"That church is a historic building that could have been catastrophic if we hadn't been alerted at that time."
Rewi said there was no damage to the inside of the church, but the exterior wall boards had been scorched.
Rewi said it appeared the fire had been deliberately lit.
"There was nothing there that would have caused the fire. Scorched patterns on the wall indicated somebody had started the fire."
A police media spokeswoman said police were called to the scene after firefighters reported the blaze may have been deliberately lit.
"It looks as though inquiries are ongoing," the spokeswoman said.