Iranian officials investigating a huge explosion at a strategic port in southern Iran have said they found “false statements” in the documentation for the shipment believed to have triggered the blast, which the authorities say has now killed 70 people.

The explosion on Saturday at the Shahid Rajaee port, Iran’s largest, triggered a fire that lasted for hours and emitted towering columns of black smoke, according to local authorities.

A statement released on Monday by the government committee investigating the blast said it had found evidence of “failure to observe safety principles.” It added that investigators were seeking to identify those behind what it described as “false statements” in the documentation of the cargo.