BEIJING — Most of the 458 people aboard a chartered cruise ship in China were still missing on Tuesday morning, more than a dozen hours after the vessel sank during a torrential rainstorm along the central Yangtze River, according to a report by Xinhua, the state news agency.

Just 13 people had been rescued, local news media reported, making this perhaps the worst passenger maritime disaster in East Asia since the sinking of the South Korean ferry Sewol last year.

The water where the boat sank is about 50 feet deep. Rescuers could hear the sounds of people trapped inside, according to a Twitter post by China Central Television, the main state network. The ship, whose name translates as Oriental Star, was crossing Hubei Province in the middle of the country when it sank at 9:28 p.m. on Monday, Xinhua reported, citing the Yangtze River Navigation Administration. Rescue work was hampered by strong winds and heavy rain.

Most of the passengers were 50 to 80 years old and had been traveling on a group tour, according to Hubei Daily. The newspaper reported that one body, which appeared to be that of a tour guide, had been discovered. Hundreds of soldiers and police and paramilitary officers were on the scene. More than 100 boats and divers were also there, the newspaper reported. The ship had capsized, with part of the hull above the surface of the water.

Prime Minister Li Keqiang arrived Tuesday, Xinhua reported. News organizations reported that Xi Jinping, the country’s president and Communist Party leader, had “issued important instructions immediately” to direct rescue operations, an indication of how seriously the party regarded the accident.

The captain and an engineer were detained by the police, Xinhua reported on one of its social media accounts, citing the river administration authorities. The report did not say why they were being held, or whether that was a routine procedure in the investigation.

Image A relative of passengers who were on a capsized cruise ship heard news of the disaster outside a travel agency in Shanghai on Tuesday. Credit... Agence France-Presse — Getty Images

According to Xinhua, the authorities learned of the disaster after several survivors swam to shore and alerted them. At least eight people were reported to have been hospitalized.

The Chinese Navy was sending a contingent of more than 140 divers to the site of the capsized ship, the Twitter account of the state-run People’s Daily reported. People’s Daily also reported that a 65-year-old woman had been rescued early Tuesday afternoon, more than 15 hours after the ferry sank. It was not clear where she had been found. People’s Daily originally reported that the woman was 85 years old.

The ship had been hired by the Shanghai Xiehe Tourism Agency to carry hundreds of retirees on a multiday trip along a long, scenic stretch of the Yangtze. A handwritten sign posted on the company’s door on Tuesday said the head of the company had gone to the scene. A mobile number scrawled on the sheet was busy throughout Tuesday morning.

Some relatives of the passengers were furious that they learned about the accident through news reports and not directly from the travel agency, according to a report by The Paper, an investigative news organization.

The people on board included five employees from one or more travel agencies and 47 crew members.

The vessel sank in Jianli County in Hubei Province. It was sailing between two of China’s largest cities, from Nanjing, the capital of Jiangsu Province, on the east coast, to Chongqing, an interior metropolis. That journey takes several days.

Both the captain and the chief engineer, who were questioned separately by the police, said the ship was suddenly struck by a tornado and capsized, Xinhua reported.

In Chinese, the term for tornado, longjuanfeng, is used more loosely than Americans use its English equivalent. One report in a Chinese newspaper said that a “tornado,” with winds of about 50 miles per hour, had struck the area around the time the ship was reported to have capsized. Winds of that strength are associated with twisters near or below the lowest rung on the six-level scale used in the United States to measure tornadoes.