BOULDER CITY, Nev. (AP) — No one was injured when a transformer at Hoover Dam briefly caught fire Tuesday morning, officials said.

“There is no risk to the power grid and power is still being generated,” according to Jacklynn L. Gould, the Bureau of Reclamation’s regional director for the Lower Colorado Region.

The fire ignited around 10 a.m. and was extinguished about half an hour later, she said.

Videos posted on social media showed what appeared to be a fire or explosion in a building near the base of the dam.

A huge plume of black smoke swirled above the building.

touring the #hooverdam and heard an explosion #fire pic.twitter.com/1tjWuNWBaZ

— Kristy Hairston (@kristynashville) July 19, 2022

The city of Boulder City posted on its Twitter account that the fire was extinguished before the fire department arrived. It referred additional questions to the Bureau of Reclamation and Hoover Dam.

The cause of the fire is under investigation.

Hoover Dam is located in the Black Canyon of the Colorado River on the border between Nevada and Arizona.

According to the federal Bureau of Reclamation, the dam is 726 feet (221 meters) tall and 660 feet (201 meters) at its base, as long as two footballs fields measured end-to-end.

As many as 20,000 vehicles a day drive across the 45-foot (14-meter) wide top of the dam, which is a National Historic Landmark.