A fire broke out around midnight Monday night in electrical equipment below the sidewalk at 18th and L streets NW. (Twitter: DC Fire and EMS)

A fire that broke out around midnight Monday in electrical equipment below the sidewalk at 18th and L streets NW caused that intersection to be closed during Tuesday’s morning rush hour, authorities said.

Drivers were advised to avoid the area.

Flames and thick smoke billowed from an underground vault early Tuesday just outside a clothing store and an office building.

The flames leaped about 10 feet into the air above a street still glistening with moisture from Monday night’s rain. The blaze appeared to break out near the southwest corner of the intersection, which is near both Connecticut Avenue and the K Street corridor.

The D.C. Fire and EMS department described the blaze as a major transformer fire.

Crews from Pepco arrived around 1 a.m. at the scene and cut power to the device.

By 2:30 a.m., D.C. firefighters said in a Twitter message that the fire had been extinguished and their units had left the scene. No one was injured in the incident.

The cause of the fire was not immediately known and crews were still “assessing the situation,” according to Pepco spokesman Marcus Beal. However, transformers can build up large quantities of heat. Summer air conditioning operations may place high demands on transformers, which step down voltages from those used with feeder and transmission lines to those used for interior wiring.

By Tuesday morning, about 100 Pepco customers were without power. Most of those were office buildings in the area. Beal said Tuesday morning that there was no estimated time for when the power would be restored.