A massive explosion and fire rocked a port on Saturday in southern Iran purportedly linked to a shipment of a chemical ingredient used to make missile propellant, killing 14 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 US met on Saturday in Oman for the third round of negotiations over Tehran’s rapidly advancing nuclear programme.

No one in Iran outright suggested that the explosion came from an attack. However, even Iranian Foreign Minister Abbas Araghchi, who led the talks, on Wednesday acknowledged that “our security services are on high alert given past instances of attempted sabotage and assassination operations designed to provoke a legitimate response”.

Iranian Interior Minister Eskandar Momeni gave the casualty figure to state media. But there were few details on what sparked the blaze just outside of Bandar Abbas, which burned into Saturday night, causing other containers to reportedly explode.