No one was hurt and no merchandise was damaged when a fire broke out Tuesday morning in a construction area on the roof of Macy’s at Minnetonka’s Ridgedale Center.

Fire officials said the cause has yet to be determined, but that the investigation will focus on construction activity, such as welding, atop the store, which is undergoing a major expansion as part of a mall restructuring.

The fire, which resulted in evacuation of the store and its Lakeshore Grill, was reported about 10 a.m., according to Macy’s spokeswoman Andrea Schwartz. It was contained just after noon, and the store reopened about 1:15 p.m. The Lakeshore Grill will remain closed for a couple of days until it can undergo inspection, Schwartz said.

Minnetonka, Hopkins, St. Louis Park, Wayzata, Chaska, Excelsior and other area fire departments responded to what a Minnetonka city spokeswoman called a report of “light and smoke” in the northwestern side of the construction area. The fire covered a 50-foot-by-50-foot area on the roof, according to Minnetonka Deputy Fire Chief Kevin Fox.

Fox said firefighters were alerted by construction workers that there was smoke in the area and were already on the scene when smoke detectors went off in part of the store. The fire spread quickly via Styrofoam in the walls and at first firefighters had trouble getting at it, he said.

Water from firefighters’ hoses poured off the roof, froze and created an ice slick in part of the mall’s sprawling parking lot.

Even as firefighters worked, shoppers were still able to enter the mall through other doors.

The blaze came during the busiest shopping week of the year. But in the end, the store was closed for only a few hours and will be open as scheduled for the rest of the week.