Police said on Thursday that an explosion struck a biodiesel fuel production plant in northern Spain on Thursday, killing two people and evacuating 250 children who were on a nearby field trip.

A police video of the explosion showed flames engulfing the plant in the northern La Rioja area, causing large columns of black smoke to rise into the sky.

Police said the two dead were workers at the plant and emergency workers rushed to evacuate the area, including a nearby park.

Police said in a statement: "A few meters from the plant, there was a field trip of 250 children who were moved from the danger zone to another area."

Reportedly, none of the children were injured, and officials are investigating the cause of the explosion. The Calahorra municipality, where the plant is located, said on Twitter that it cordoned off a one-kilometer perimeter around the plant as emergency officials work to contain the fire.

Mayor Elisa Garrido wrote on Twitter: "The situation is under control at this moment." The plant and industrial area have been completely evacuated.