A downtown Knoxville building caught fire Tuesday morning off Market Street.Fire crews said people reported smoke coming from the building at 713 Market Street around 6:30 a.m. The building houses a few law offices and no one was inside the building at the time of the fire. According to the Knoxville Fire Department, first responders found the fire in a second story wall. The fire was quickly put out and crews are unsure how it started as of right now. Firefighters said the sprinkler system held the fire at bay until they could arrive. The building suffered significant water damage.