Unapproved, combustible resins used in a decorative band on upper floors fueled a Jan. 25 fire at a Las Vegas resort, Clark County officials say.

The Monte Carlo hotel-casino's three-alarm blaze caused $100-million in damage and lost business. There were no major injuries. A county investigation ruled the fire unintentional and no penalties were levied against Las Vegas contractor, Union Erectors, LLC.

Related Links: Report on the Monte Carlo Fire

Welders working for the contractor atop the 32-story resort rooftop dropped molten steel fragments from a handheld torch. The fire spread across a 20-ft-tall parapet and parts of the south and west facades before being extinguished.

Clad in an Exterior Insulation Finish System, the Monte Carlo is a cast-in-place structure completed in June, 1996 by M.J. Dean Construction of Las Vegas. The decorative bands that fueled the flames, however, were created with a polyurethane resin coated expanded polystyrene (EPS) foam. Those parts of the building didn't meet county codes.

According to a report by Baltimore-based fire engineer, Hughes Associates Inc., the resins on the two upper-level decorative bands accelerated the fire. Some areas had lamina 28% to 69% thinner the 3.2-mm required minimum. Lamina is an exterior coating that is made of a base coat of resin, a layer of fiberglass mesh, and a top finishing coat.

"It's entirely possible that the lamina, exposed to the elements, could have just shrunk over the years," says Dan Kulin, a county spokesman. "However, the thickness issue didn't play a role in starting or spreading the fire. It was simply a finding from the report."

MGM Mirage, Inc., the hotel-casino's owner, must hire a Nevada-registered fire protection engineer to recommend remedies to the flaws found in the report.