(AP) — Diesel fuel has ended up in some vehicle gasoline tanks in northeast Nebraska.

Six gas stations in Norfolk, O’Neill and Columbus mistakenly received diesel in their gasoline tanks after an error at the NuStar Energy pipeline terminal.

NuStar spokeswoman Joanna Weidman says the company is removing the contaminated fuel from the gas stations and replacing it with gasoline.

NuStar also plans to cover the cost of any repairs to vehicles affected by the mix-up.

Brian Johnson of Casey’s General Store told the Norfolk Daily News that NuStar contacted Casey’s after it realized the problem, but some customers had already pumped contaminated gas into their vehicles. Two Casey’s locations in Norfolk and one in O’Neill were affected.

Weidman says NuStar is investigating what happened to prevent a recurrence.