Thick smoke filled the air when an underground transformer exploded about 11:20 a.m. last Friday near 6th and Main streets in Downtown. Multiple explosions followed, sending flames through some manhole covers as high as 20 feet in the air. Dominion Virginia Power switched off electricity in the area to prevent further explosions. About 400 people were evacuated from nearby buildings, with a few people treated at the hospital for smoke inhalation. The temporary power outages caused some businesses to close for the day.