Casselton - Authorities urged residents to evacuate a US town after a mile-long train carrying crude oil derailed, shaking residents with explosions that sent flames and black, hazardous smoke into the sky.The Cass County Sheriff's Office said the National Weather Service was forecasting a shift in the weather. "That's going to put the plume right over the top of Casselton," Cass County Sheriff Paul Laney said. The town has about 2 400 residents.No one was hurt in Monday's derailment, and the cause was being investigated.About two-thirds of the town's residents had evacuated their homes, Sheriff's Deputy Joe Crawford said early on Tuesday.The derailment in North Dakota, the country's No 2 oil-producing state, happened amid heightened concerns about the United States' increased reliance on rail to carry crude oil.Fears of catastrophic derailments rose after the July crash in a Quebec town of a runaway train carrying crude from North Dakota's Bakken oil patch. Forty-seven people died in the ensuing fire.The number of crude oil carloads hauled by US railways surged from 10 840 in 2009 to a projected 400 000 this year. Despite the increase, the rate of accidents has stayed relatively steady. Railways say 99.997% of hazardous materials shipments reach destinations safely.North Dakota's state's top oil regulator has said he expected as much as 90% of the state's oil would be carried by train in 2014, up from the current 60%.Investigators couldn't get close to the burning train outside of Casselton. BNSF Railway said it believes about 20 cars caught fire after its oil train left the tracks on Monday afternoon. The sheriff's office said it thinks 10 cars were on fire.Avoid smokeThe National Transportation Safety Board said it has launched a team to investigate the accident.The railway tracks pass through the middle of Casselton, and Cass County Sheriff's Sgt Tara Morris said it was "a blessing it didn't happen within the city."Morris said it could take up to 12 hours before authorities could get close to the fire.In the initial hours, authorities told residents to stay indoors to avoid the smoke.Hannah Linnard, 13, said she was at her friend's house about 800m from the derailment."I looked out the window and all of a sudden the train car tipped over and the whole thing was engulfed in flames and it just exploded. The oil car tipped over onto the grain car," she said.She could feel the warmth even inside the house.