Corpus Christi, (WBAP/KLIF) – Seven contract workers were injured Saturday when a storage tank exploded at a petroleum facility in Corpus Christi. Four of the victims were critically injured. Magellan Midstream Partners Operations Manager Mark Calhoun says the tank holding crude oil was being cleaned when a fire began. The fire caused an explosion. It is not yet known what caused the fire. Corpus Christi deputy Fire Chief Richie Quintero says the four most critically burned workers are now hospitalized in San Antonio. The remaining three suffered mainly minor injuries, and were treated and released from hospitals in Corpus Christi.