Multiple patients are being treated at University of Iowa Health Hospitals & Clinics for injuries following an explosion and fire at a Marengo plant.The city is telling residents to stay indoors due to the poor air quality. The city also says to avoid the 800 block of East South Street.KCCI has sent a crew to the scene, where we captured footage of crews responding. Video footage shows heavy smoke and flames.This is a developing story. Stay tuned to KCCI on-air and online for updates.Watch: Explosion and fire in Marengo