DOON, Iowa (AP) — Some northwest Iowa residents have been evacuated following a train derailment that caused a crude oil leak. The Sioux County Sheriff’s Office said Friday that residents living along a rural road south of Doon have left their homes. Sheriff Stewart Vander Stoep in neighboring Lyon County says the train derailed between 5 and 5:30 a.m. Friday just south of Doon. He says it’s unclear how much oil has leaked.

It’s also unclear how many cars derailed and what caused the derailment. A BNSF spokesman didn’t immediately return a call from The Associated Press. Floodwater along the Little Rock River is running over a road north of the track. Evacuations have occurred downstream at Rock Valley, where the Rock River is expected to crest later today (Friday). The Little Rock flows into the Rock River.