BOULDER CITY, Nev. (AP) — A transformer exploded at Hoover Dam, producing a thick cloud of black smoke and flames that quickly were extinguished. Authorities say no one was hurt in Tuesday’s explosion and electricity continued to flow to the 8 million people in Arizona, Nevada and Southern California who rely on it. The U.S. Bureau of Reclamation says the fire ignited around 10 a.m. and was put out within 30 minutes. Hoover Dam is located on the Nevada-Arizona border about 25 miles southeast of Las Vegas. It’s a popular tourist destination. Some visitors captured the fire and smoke on video and quickly shared it on social media.