A transformer fire caused a small explosion at Hoover Dam on Tuesday morning, according to the Bureau of Reclamation.
Videos posted on social media showed the fire and explosion in a building near the base of the dam. A huge plume of black smoke swirled above the building.
According to the agency, the A5 transformer at the dam caught fire but was extinguished by 10:30 a.m.
No injuries were reported.
"There is no risk to the power grid. Power is still being generated from the powerhouse. We are investigating the cause of the fire and will provide additional updates as they are available," said USBR's Regional Director Jacklynn L. Gould.
Hoover Dam, located on the Nevada-Arizona border about 25 miles southeast of Las Vegas, is a popular tourist destination.
William Herro, 13, of San Francisco, was on a viewing bridge with his parents when he saw the explosion and then heard a “big boom.”
“A ton of black smoke just exploded in the air. It looked almost like a mushroom and then a fire followed,” said Herro, who posted cellphone video of it on TikTok. “I was really surprised and I started filming.”
The postings showed the explosion occurred at a building slightly downstream from the base of the dam. The complex is in the Black Canyon of the Colorado River.
According to the Bureau of Reclamation, the dam is the second-tallest in the U.S. at 726 feet. Each of its 17 generators can supply electricity to 100,000 households.
As many as 20,000 vehicles a day drive across the wide top of the dam, which is a National Historic Landmark.
