The Chiba-bound supertanker that was apparently attacked last month in the Strait of Hormuz sustained a larger impact dent, presumably from explosives, below the waterline than previously thought, the transport ministry has revealed.

Soot marks radiating from the damaged section of the ship's starboard quarter suggest something exploded near the surface of the water next to the hull.

The findings were reported Wednesday to an investigative panel of private-sector and government experts. The ministry also told the panel that a crew member heard a loud sound and felt a shock on the starboard side at the time and saw a descending red flash.