The captain of a cruise ship that slammed into a volcanic reef before sinking off the Aegean island of Santorini blamed strong currents for the accident, Greece's state-run television said Sunday. The 1,156 passengers, most of them Americans, and the 391 crew members were forced to evacuate the listing liner, which sank 15 hours after the accident on Thursday. A pair of French tourists have been missing since then. On Saturday, the captain and five other officers of the 489-ft. Sea Diamond were indicted on charges of causing a shipwreck through negligence, breaching international shipping safety regulations, and polluting the environment. All were released pending further investigation, but judicial officials said their indictments would eventually encompass charges relating to the disappearance of the two French passengers, a 45-year-old father and his teenage daughter, who are presumed dead. If convicted, the officers each face a maximum five-year sentence. The Greek-flagged cruise ship rammed a well-marked and charted reef in fair weather on Thursday, inside Santorini's sea-filled crater. Louis Cruise Lines, the Cypriot firm that runs the ship, insisted that the Sea Diamond was equipped with all the latest navigation technology. While all other passengers were retrieved safely, several tourists complained of insufficient supplies of life vests, little guidance from crew members, and a delayed, four-hour evacuation process that forced some passengers to climb down rope ladders. Greek authorities have vowed to come down hard on those found accountable.