The National Weather Service will send an investigator into southern Rowan County today to determine whether the storm which roared through the area Monday evening was a tornado.No injuries were reported, but there was significant damage near the town of China Grove.The storm struck about 6:45 p.m., after a severe thunderstorm warning had been issued.Rowan County officials said the damage stretched over a path five to eight miles long, but the worst was along Goodnight Road and the U.S. 29 area near China Grove.Grove Supply, which provides building supplies throughout the area, was heavily damaged. Winds blew the roof off a warehouse at the company, and portions of the roof landed about 100 feet away. Portions of walls at the company also were blown in.Meteorologists say severe thunderstorms sometimes can cause similar damage, as their winds can approach or exceed 80 mph.The storm initially knocked out power to about 1,800 Duke Energy customers. By sunrise today, power had been restored to all but about 220 of those customers.