An investigation is underway to determine the cause of a fire that inflicted heavy damage to a popular Glocester eatery. The fire broke out early yesterday morning in the bar room at Snow's Clam Box on Putnam Pike. The fire was reported to authorities by a woman who lived upstairs with her son, and both escaped safely. It took around an hour for several responding fire departments to bring the blaze under control. The investigation is being handled by the state Fire Marshal's Office.