A tour bus with dozens of international tourists suddenly caught fire Monday as it was leaving the Hoover Dam Visitor Center near the Arizona and Nevada border, officials said. The driver, a tour guide and 59 passengers got off the bus before it was consumed by the fire, said Rose Davis, a spokeswoman for the U.S. Bureau of Reclamation in Boulder City. The bus had exited a parking lot on the Nevada side of the Hoover Dam when the driver smelled smoke and saw fire at about 4 p.m., Davis said. The driver grabbed a fire extinguisher that was on the bus and tried to combat the flames, but quickly realized the bus had to be evacuated, Davis said. "It engulfed the bus fairly quickly," she said. The unexplained accident caused some congestion as the Hoover Dam closed late Monday, but Davis said the attraction would be open to visitors during its normal business hours Tuesday. The accident occurred on a mountain road along U.S. 93 near the Mike O'Callaghan-Pat Tillman Memorial Bridge, the only road connecting southern Nevada and Arizona, said Nevada Highway Patrol Trooper Loy Hixson. Traffic on the bridge was not affected by the fire, he said. A tow truck had been called to pick up the charred vehicle. The tour operator, Bravo Express, sent a new bus to pick up its passengers within hours of the accident, Davis said. It was unclear what country the visitors were from. Officials with the California-based tour company declined to comment Monday. Investigators were looking into the cause of the fire. Generally, vehicle fires that begin and burn so quickly involve an engine problem, Hixson said. The region's dry, mountainous weather can cause overheating in vehicles that are not regularly maintained, he added. "These are pretty steep roads out here and you need to have your car in shape," Davis said.