SOUTH SIOUX CITY, Neb. (AP) _ Authorities have not let people who live nearest a northeast Nebraska grain elevator damaged in an explosion return to their homes, fearing the structure could collapse at any moment. Tuesday’s blast blew a gaping hole into the Anderson Farms elevator in South Sioux City, injuring two people. City Police Chief Ed Mahon said that the structural integrity of the 230-foot tower is uncertain. Officials hope to tear down the elevator in a controlled fashion before it falls on its own. The evacuation zone has been reduced, so some people have gone back to their homes. Large steel cargo containers will be placed along streets to help protect homes from debris if the tower were to collapse.