One worker died and four others were injured in an explosion at an ethanol plant in eastern Nebraska.

The explosion was reported Monday afternoon at a Green Plains ethanol plant in Wood River, which is about 160 miles west of Omaha. The Nebraska State Fire Marshal Agency said firefighters found a liquid holding tank that had been damaged in the explosion at the plant, which makes the highly flammable fuel additive. There was no fire when they arrived.

One worker was in critical condition Tuesday at an Omaha hospital. Three others were treated for minor injuries at a local hospital and released.

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The State Fire Marshal’s office the explosion was an accident caused by the work that was being conducted at the time. It is not believed to be linked to a separate fire at the plant that happened last Friday.

A Green Plains spokeswoman said the explosion happened during routine maintenance and repairs on the tank. The plant wasn’t operating at the time.

The company spokeswoman said Green Plains officials were "deeply saddened" about the death.

The names and ages of the person who died and the injured workers were not immediately released. An autopsy is planned.