Sixty-foot flames towered above a biofuels plant in eastern Iowa after an explosion Wednesday morning, local media report.

At 4:16 a.m., the explosion disrupted operations at Hero BX Biofuels in Clinton, Iowa. Firefighters arrived to find massive flames rising from a structure fire at the southwest corner of the plant, the Clinton Herald reports.

The immediate concern was that flames would reach the plant’s methanol tank, firefighters said. Responders commenced cooling operations to protect two threatened tanks

Fire operations expanded into a mutual aid response with firefighters from nearby Comanche, Low Moor in Iowa and Fulton, Illinois.

Available water proved to be an issue. Firefighters were forced to use tankers to shuttle water to the fire scene.

Hazardous materials specialists responded to the scene to deal with heat transfer oil spilled during the fire.

All Hero BX Biofuel employees were safely evacuated. Firefighters were on the scene more than four hours.