A fire broke out at Riverhead Trailer on Flanders Road in Riverside about 8:20 p.m. Wednesday.
The Riverhead Fire Department responded, with assistance from the Flanders Fire Department, which provided a rapid intervention team, which steps in when a firefighter is trapped, and the Jamesport Fire Department, which stood by at the Riverhead firehouse, according to Riverhead Fire Chief Nick Luperella.
The building, which houses a business that sells boat and cargo trailers, fronts Flanders Road and is adjacent to a mobile home park. It was not occupied at the time of the fire, according to police. The fire department shut down a section of Flanders Road while it fought the blaze.
Southampton Town fire marshals John Rankin and Brian Williams said the fire sparked after the business owner put ashes from a wood-burning stove on the premises into a plastic container, which later ignited.
The blaze was contained to one room in the building, fire officials said.