AUSTIN, MN --A tour bus returning from an Iowa casino ran off a southern Minnesota interstate and rolled over in a ditch Wednesday, killing two people and injuring 21, authorities said. The bus, operated by Strain Bus Line Motorcoach Tours in Rochester, was eastbound on Interstate 90 just west of Austin when it crossed into the westbound lanes and flipped over about 3:20 p.m., Department of Public Safety spokesman Andy Skoogman said. Passenger Ardell Swenson, 71, of Austin, said she was just putting her head back to rest when the bus crashed. "When I got myself organized there was all kinds of red and white and blue lights flashing," she said. "There was glass all over." The bus was carrying 23 people including the driver. Capt. Matt Langer, a state highway patrol spokesman, said injuries ranged from minor to critical. Details about those killed were not immediately released. Langer said the bus had no seat belts, and when it overturned, some passengers were trapped underneath. Rescue crews were forced to pull off the bus's windshield because the 47-passenger coach had settled on its right side, blocking the door. Several people sat in the grass at the scene, many bleeding from what appeared to be minor wounds but talking to medical personnel. The driver was in serious condition Wednesday night at St. Marys Hospital in Rochester, where two passengers also were in critical condition. Langer said the driver had been interviewed but investigators had not determined the cause of the crash. Eight of 14 passengers taken to Austin Medical Center also remained hospitalized Wednesday night, as did three of six people taken to Albert Lea Medical Center. Hospital officials said no further information would be released until Thursday morning. Swenson was treated at the Austin hospital for what she called minor injuries. "I'm just going to be really sore," she said. Strain Bus Line operates a bus every Wednesday from Rochester to Diamond Jo Casino in Northwood, Iowa, charging $15 a seat, according to its Web site. Messages seeking comment were left on the bus line's voicemail. Northwood is about 30 miles southwest of Austin. The highway patrol said the road was clear and dry at the time of the accident. Bold Lines Inc., which does business under the name Strain Tours, is a small operator with six drivers and four buses and has had no accidents in the past two years, according to the Federal Motor Carrier Safety Administration Web site. In 2002, Bold Lines paid $20,000 to settle an enforcement case over drug testing for drivers, according to the federal safety agency. It also paid $300 to settle a case over driver duty times and recordkeeping. The agency has advised roadside inspectors to inspect the company's vehicles because of safety concerns, according to the Web site. Its "Inspection Selection System" rated Strain at a 76, with any score between 75 and 100 meaning an inspection is warranted.