A transformer exploded Tuesday at Hoover Dam, producing a cloud of thick, black smoke and flames that were quickly extinguished. No one was hurt and electricity continued to flow from one of the nation’s largest hydroelectric facilities, authorities said.

“There is no risk to the power grid,” according to Jacklynn L. Gould, the federal Bureau of Reclamation’s regional director for the Lower Colorado Region. The fire ignited around 10 a.m. and was out within a half-hour, she said.

Hoover Dam, located on the Nevada-Arizona border about 25 miles (40 kilometers) southeast of Las Vegas, is a popular tourist destination and some of the visitors captured the scene on video and quickly shared it on social media.

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.

The cause of the fire is under investigation and it’s not clear how extensive the damage was to the transformer.

According to the Bureau of Reclamation, the dam is the second-tallest in the U.S. at 726 feet (221 meters). 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.

(AP)