A stretch of road in downtown Washington has been closed after a large transformer fire broke out underground.

The District of Columbia Fire Department says the fire occurred early Tuesday at 18th and L streets northwest as smoke billowed from an underground vault outside a clothing store and an office building. Firefighters said the flames were extinguished by 2:30 a.m. No injuries were reported. The cause wasn't immediately known.

Pepco spokesman Marcus Beal says about 100 customers are without power in the area. He says there's no estimate for when power will be restored.

The Federal Reserve said in a statement that office space it leases nearby has been without electricity, but no essential operations are affected. Employees who can telecommute are working from home.