A massive explosion and fire rocked a port Saturday in southern Iran purportedly linked to a shipment of a chemical ingredient used to make missile propellant, killing eight people and injuring around 750 others.Helicopters dumped water from the air on the raging fire hours after the initial explosion, which happened at the Shahid Rajaei port just as Iran and the U.S. met Saturday in Oman for the third round of negotiations over Tehran’s rapidly advancing nuclear program.IRAN, US BEGIN NEGOTIATIONS OVER TEHRAN'S ADVANCING NUCLEAR PROGRAMNo one in Iran outright suggested that the explosion came from an attack. However, even Iranian