The White Swan Hotel in Greytown was briefly evacuated on Friday night after an employee noticed a burning smell coming from somewhere inside the building.
Greytown fire chief Steve Meyrick said a small number of guests were evacuated about 11.30pm, while fire crews from Masterton and Greytown used a thermal imaging camera to try to track down the source of the smell.
It was eventually traced to an electrical fault in the office, Mr Meyrick said.
"It was a UPS battery back-up for a computer that's decided to have a meltdown."
Traffic on Main St was briefly reduced to one lane with stop/go signs while fire crews checked the building.