The captain and five other crew members from the Sea Diamond already have been charged with negligence.
The ship struck well-marked rocks on April 5 and sank near Greece's Santorini island.
Nearly 1,600 people, most of them Americans, including two dozen students from North Carolina, were safely evacuated. An unmanned submarine is searching the sunken vessel for a missing French tourist and his daughter.
"The incident was a result of human error - but so are 75 percent of all accidents at sea," said Giorgos Koubenis, a representative of Cypriot-based Louis Cruise Lines.
It was the company's first comment on the probable cause of the accident.
Koubenis said the Sea Diamond was one of the company's premier ships. "We only acquired it last year," he said.
The Greek government stepped up efforts to stem an oil leak from the Sea Diamond, which has already spilled more than 26,000 gallons of fuel near Santorini, known for its soaring cliffs and black sand beaches. Nearly 119,000 gallons of oil are still inside the ship, threatening environmental damage at the onset of the busy summer season. The remote-controlled submarine was trying stop the leak. Efforts were hampered by the ship's unstable position. The 10-story-high vessel is face-down on an undersea slope, with most of the hull more than 325 feet below the surface. "Santorini must return to the way it was before the accident," said Merchant Marine Minister Manolis Kefaloyiannis, adding that additional resources had been made available for the cleanup. "The situation is under control for the moment." In a statement to the Cyprus stock market, the Louis Cruise Lines said it was fully cooperating in efforts to investigate the accident and had hired a private firm to help prevent environmental damage. The company said it was fully insured, including for possible environmental pollution. The captain has told investigators he was caught unawares by a sea current that swept his vessel onto the rocks minutes before it was due to dock. If convicted of negligence, the captain, first mate and four other crew members face a maximum five-year sentence. The Greek captains' association spoke out in defense of the crew. "Once again, the captain has been made a scapegoat and has been blamed even before his account (was heard," the Masters and Mates Union of the Greek Merchant Marine said in a statement. "The captain is a very capable and highly regarded colleague," the union said. "Of course the fact that two passengers were not found fills us with sadness. (But) the evacuation was carried out successfully." The association cited a 2003 study by the National Technical University of Athens, which listed Santorini of one of 17 Aegean Sea ports lacking proper docking facilities. The Sea Diamond sank in Santorini's sea-filled volcanic crater - known as a caldera - about 15 hours after the rocks tore a hole nearly 100 feet long in the side of the ship. Missing French tourists Jean-Christophe Allain, 45, and his 16-year-old daughter Maud had a lower deck cabin near the position whether reef struck. Allain's wife and son survived the accident. AP-CS-04-11-07 1212EDT