Transformer Explodes at Hoover Dam

A transformer exploded at the Hoover Dam Tuesday morning, causing a fire that authorities say was quickly extinguished with no interruption to the flow of power from the massive hydroelectric plant. Authorities say nobody was injured in the explosion and fire around 10am and the power grid was never at risk, the Las Vegas Review-Journal reports. The Bureau of Reclamation, which operates the dam and powerhouses, tweeted that it was able to extinguish the fire by 10:30am. The transformer is one of 15 at the facility on the Arizona-Nevada border.

The explosion and fire sent plumes of smoke into the air. Tourists said they heard an alarm and felt the ground rumble. William Herro, a 13-year-old visitor from, San Francisco, tells the AP that he saw the blast from a viewing bridge and 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," he says. "I was really surprised and I started filming." Authorities saying they are trying to determine the cause of the blast and the extent of the damage. (More Hoover Dam stories.)