WESTBROOK – Operators of a new natural gas-fired plant offered assurances that the firing of a turbine and boiler that created acrid smoke as far away as South Portland was a one-time occurrence.

The test firing of one of the plant’s two turbines Friday night sent the cloud rolling over Portland. Several residents who believed there was a fire dialed 911 or called the fire departments in Portland and South Portland.

The turbines and boilers like those at Calpine’s Westbrook Energy Center have preservatives to keep the components from rusting.

The smoke was created by the burning of preservatives, paint primer and some plastic used to preserve insulation when the turbine and steam generator system went on line for the first time, said Plant Manager William Vogel.