Ill-fated cruise ship owner to answer questions Questions remain about why the Costa Concordia hit rocks on Friday At least 6 people died and about 16 are not accounted for Divers are searching in pitch blackness for the missing The cruise ship owner says the captain made significant errors Giglio, Italy (CNN) -- The owner of the cruise ship that hit rocks and flipped onto its side over the weekend, leaving at least six people dead, will speak to the media Monday morning, and may clear up questions about what caused the disaster. Divers continue to search the skyscraper-sized ship, working underwater in pitch blackness, in hopes of finding about 16 people still missing after the wreck. There were roughly 4,200 people on the Costa Concordia when it ran aground Friday evening off the Italian island of Giglio. The captain of the ill-fated cruise ship may have made "significant" errors that led to wreck, the cruise line said late Sunday. The ship's captain, Francesco Schettino, was detained Saturday for alleged manslaughter, causing a shipwreck and abandoning ship while passengers were still on board, chief prosecutor Francesco Verusio told Italy's ANSA state news agency. Schettino joined Costa Cruises as a safety officer in 2002 before being appointed captain four years later, the company said. First officer Ciro Ambrosio was being detained for questioning on similar charges, prosecutor Verusio said. Even with its admission that mistakes were made, the Genoa-based cruise company -- whose parent firm, Carnival Corp., did not respond Sunday to requests from CNN for more information -- defended the ship's crew in the face of criticism. "It is becoming clear that the crew of the Costa Concordia acted bravely and swiftly to help evacuate more than 4,000 individuals during a very challenging situation," the company said, adding all crew members are trained and the passengers earlier took part in an evacuation drill. Survivors have described the scene -- after the ship hit rocks near Giglio, off the coast of Tuscany, and turned over on its side -- as "chaos." "It was just battling, mad scrambles," American student Brandon Warrick said of the fight to board lifeboats, describing it as "a giant every man for himself." His sister Amanda said she feared she was going to die as they waited for up to two hours for rescue. Waiting was definitely the worst. Because we didn't know who was going to be coming, how much longer we would have to wait," she said. Authorities have said at least 20 were injured due to the incident, in addition to those killed. That death toll includes two elderly people whose bodies were found, with their life jackets on, near one of the ship's restaurants, Italian Coast Guard spokesman Capt. Cosimo Nicastro told reporters Sunday. Hours earlier, crews rescued a ship employee trapped in a ship restaurant. The man -- an Italian purser whose name was not released -- was suffering from hypothermia when rescue crews found him, said Commander Filippo Marini, a spokesman for the Port Authority of Porto Santo Stefano. Authorities are reviewing passenger lists to confirm the exact number of missing people, said Giuseppe Orsina, a spokesman with the local civil protection agency. The U.S. Embassy in Italy, on its Twitter feed, said two of the 120 Americans who were aboard the ship still had not been accounted for. It was not clear Sunday as to the nationalities of other missing people, with CNN affiliates having reported Italians, Peruvians, Brazilians, French and Britons were all represented on the ship. All 109 Russians on board have been accounted for, the Russian Foreign Ministry announced late Sunday. There were fears the death toll could rise as rescuers searched the ship, which was nearly 50% submerged and had a gash in its hull, authorities said. As the search for survivors continued Monday, questions and criticism continued about what caused the shipwreck and the adequacy of the response. Speaking on Italian television, the ship's captain insisted the rocks that the Concordia hit were not marked on his map. "On the nautical chart, it was marked just as water," Schettino said, adding that the ship was about 300 meters from shore. But Nicastro, the Coast Guard spokesman, insisted that the waters where the ship ran aground were well-mapped. "Every danger in this area is on the nautical chart," Nicastro said. This is a place were a lot of people come for diving and sailing. ... He said the Coast Guard was investigating why the ship took the course it did. "We know where the ship was," he said. We know it was too close to the island. ... We don't know why. Costa Cruses said Sunday that it can only access that information with authorities' permission. Built in 2006, the Concordia had been on a Mediterranean cruise from Rome with stops in Savona, Marseille, Barcelona, Palma de Mallorca, Cagliari and Palermo. The ship was carrying about 3,200 passengers and 1,000 crew members when it ran aground and began taking on water Friday night. The crew kept going because they believed the vessel could continue sailing normally, said Nicastro. Authorities are looking at why the ship didn't send a mayday during the incident. CNN's Alexander Felton, Marilia Brocchetto, Livia Borghese, Hada Messia, Michael Martinez, Melissa Gray, Phil Gast, Chelsea J. Carter and journalist Barbie Nadeau contributed to this report.