Mexican authorities say at least 12 people died when a bus carrying foreign tourists to Mayan ruins in eastern Mexico flipped over on a highway. Quintana Roo state Civil Defense spokesman Vicente Martin says that at least seven Americans and two citizens of Sweden are among the injured. Authorities haven't yet established the nationalities of the dead. Video images from the scene show the bus on its side in vegetation off the highway, with some survivors lying on the pavement while others walked around. Martin says Tuesday's crash occurred as the bus was on its way to the ruins at Chacchoben, about 110 miles south of Tulum. The cause of the accident is under investigation.