Giglio, Italy (CNN) -- The captain of the ill-fated Costa Concordia may have made "significant" errors that led to the vessel's wreck Friday and subsequent deaths of at least five people, the cruise line said late Sunday.
"The route of the vessel appears to have been too close to the shore, and the captain's judgment in handling the emergency appears to have not followed standard Costa procedures," Costa Cruises said in a statement.
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 himself 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 the island of Giglio, off the coast of Tuscany, and turned over on its side -- as "chaos."
"It was just battling, mad scrambles," U.S. 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.
Earlier Sunday, before the two bodies were found, Giglio Mayor Sergio Ortelli said at least six ship workers and 11 passengers still had not been located.
Authorities are reviewing passenger lists to confirm the exact number of missing people, said Giuseppe Orsina, a spokesman with the local civil protection agency. Many of those rescued in the early hours were taken to small churches and other buildings around the island for shelter. Some were still wearing the pajamas and slippers they had on, as the ship went down.
"These people could be still on the island of Giglio, in private houses or in hospitals," Orsina said.
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.
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. Local fishermen say the island coast of Giglio is known for its rocky sea floor.
"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. ... All the dangers are known."
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."
Italian prosecutors seized the ship's data recorders Saturday, and expect to analyze them within days. 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, the Coast Guard spokesman. Realizing there was a significant safety problem, the commander steered the Costa Concordia closer toward the port of Giglio, he said.
Authorities are looking at why the ship didn't send a mayday during the accident.
Besides the two elderly people, the dead include two French tourists and a crew member from Peru, port authorities in Livorno said. One of the victims was a 65-year-old woman who died of a heart attack, authorities said.
Rescuers overnight Saturday reached two South Korean passengers who had been trapped in the ship for more than 24 hours, authorities said.
"It's a miracle that we found the Korean couple alive, and we hope we'll find more people," said Nicastro of the Italian Coast Guard.
The couple, both 29, were found in a cabin after they heard rescuers calling out and managed to make contact, according to Italy's ANSA news agency. Video showed the couple, reportedly on their honeymoon, being taken ashore and loaded into a waiting ambulance.
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.