At least 101 people are missing and 78 have been injured following a submarine attack on an Iranian vessel off the coast of Sri Lanka.

Earlier, Sri Lankan authorities deployed naval and air forces to rescue Iranian sailors after their ship, the IRIS Dena, sent out a distress signal near the island, The Caspian Post reports via foreign media.

Vijitha Herath, Sri Lanka’s Foreign Minister, told parliament that the distress call came at dawn. The vessel was carrying 180 people.

Thirty injured sailors were transported to a hospital in the Sri Lankan port of Galle. The cause of the sinking remains unknown.

An opposition lawmaker raised questions about whether the ship might have been targeted amid U.S. and Israeli operations against Iran, but authorities did not provide an official response.