At least seven people were killed and nine injured Tuesday when a bus plunged off a bridge overlooking one of Rio\'s main access roads, firefighters said. \"Rescue teams are on the scene. So far seven deaths have been confirmed,\" a spokesman said. A Civil Protection statement later said nine people were injured and rushed to area hospitals. The bus landed on is its roof after falling from a height of 15 meters (45 feet) onto Rio\'s Avenida Brasil, an AFP photographer reported. The avenue was littered with blood stains and shattered glass, and some of the bodies were in large black bags, awaiting removal. Authorities have launched an investigation. Some eyewitnesses told Globo television that the bus driver was arguing with a passenger who had not paid his fare at the time of the accident. Some 50 firefighters were taking part in rescue operations, Globo quoted civil protection secretary Colonel Sergio Simoes as saying.