AMHERST — State and local fire officials said they have been unable to determine the cause of a fire Saturday that extensively damaged a building housing three employers.

The Saturday morning fire was the second in three day’s time at 8 Manhattan Drive, an industrial park building. The fire destroyed the portion of the building housing The Bread Chef bakery and the front section of Poly-Ject, a custom injection-molding company, according to a New Hampshire Sunday News article.

Cold Stone Creamiers also rents space in the building.

In a statement issued Tuesday, state and town fire officials the cause of the fire is undetermined.

However, the statement quotes Fire Marshal William Degnan saying that electrical extension cords should be used only on a temporary basis and only with portable equipment. The statement said investigators know where the Saturday fire started, but the statement did not disclose the origin.

The investigators said a Thursday morning fire in a utility room adjacent to the bakery was accidental and due to “electrical compromise.” That fire caused little damage.

A man answering the telephone at The Bread Chef would not discuss use of extension cords. He would not give his name and said he did not want to discuss his plans on the telephone.