An estimated 230,000 gallons of crude oil spilled into flood waters in Northwestern Iowa, near Doon.
While the cause for the derailment has not been officially determined, a disaster proclamation by the state's governor and local officials blamed flooding caused by two days of heavy rain for eroding the soil beneath the railroad tracks.
Drone footage released by authorities in Iowa shows oil spreading across flooded fields following a devastating train derailment.
Ken Hessenius with the Iowa Natural Resources Department says his crews will try to determine how fast the oil is being carried downstream by the rain-swollen Little Rock River.
The train derailed early Friday just south of Doon in Lyon County, leaking oil into surrounding floodwaters from the swollen Little Rock River.
Lyon County Sheriff Stewart Vander Stoep said, "About 100 people are working on this and they are making some pretty good progress, they've been hauling oil out here all day long".
Within hours of the derailment, BNSF had brought in dozens of semitrailers loaded with equipment to clean up the spill, including containment booms, skimmers and vacuum trucks.
Omaha's public water utility - Metropolitan Utilities District - said it was monitoring pumps it uses to pull drinking water from the Missouri River.
BNSF had hazardous materials and environmental experts on the scene and had begun cleanup within hours of the derailment, Williams said. The train was carrying crude from the oil sands of western Alberta to Stroud, Oklahoma.
The derailment also caused concern downstream, including as far south as Omaha, Nebraska, approximately 150 miles (240 km) from the derailment site. ConocoPhillips spokesman Daren Beaudo said each tanker can hold more than 25,000 gallons of oil. The spill reached the Rock River, which joins the Big Sioux River before merging into the Missouri River at Sioux City.
Danger from the spill has been exacerbated by recent rainfall, which has caused the Rock River to overflow its banks along the route of the train tracks.
Then an unrelated fire at an industrial site about a mile south of town took emergency crews away from the derailment.