(CNN)A luxury cruise liner, the "Dongfangzhixing" or Eastern Star, capsized late Monday in the waters of China's Yangtze River, with 458 passengers and crew on board.
The ship had been traveling from Nanjing, capital of east China's Jiangsu Province, to Chongqing city in the southwest.
As rescue workers scramble to find survivors and remains, what do we know about the tragedy so far?
At the moment, there is just speculation about the cause of the incident. The ship capsized around 9:30 p.m. June 1, during a storm in the section of the river that flows through Hubei's Jianli County, authorities said.
The captain and the chief engineer, who were among the at least 15 survivors of the incident, claimed that the ship sank after being caught in a "longjuanfeng" -- meaning cyclone or tornado -- reported the local Xinhua news agency.
The captain and the chief engineer said the ship capsized "within one or two minutes" of being trapped in extreme weather conditions, the China Daily newspaper reported. Wang Yangsheng, a senior official with the Yueyang Maritime Rescue Center, said that the incident happened "so fast that the captain did not even have the time to send out a distress signal," according to the newspaper.
However, Zhang Zuqiang, a senior official with the China Meteorological Administration, told Beijing News that he wasn't sure that there had been a cyclone, but that it had been raining heavily at the time.
The ship was not found to be overloaded and had enough life vests on board, according to the South China Morning Post (SCMP).
More details are set to emerge as the captain and chief engineer are taken into custody and questioned by police, according to state media.
Hundreds are missing from the wreck.
The SCMP also reported that officials believe five people may be trapped inside the ship's upturned hull.
"Rescuers knocked on the ship and received responses," the China Daily reported.
One elderly passenger was rescued, with state TV showing footage of rescuers cutting through the hull with an angle grinder.
Authorities say most of the passengers on board were senior citizens. Xinhua reported that of the 458 on board, 406 were passengers, five travel agency workers and 47 crew.
Quartz claims that relatives of the missing passengers have been gathering outside the Xiehe Travel agency in Shanghai, which has closed its doors with a note saying that members of its staff are busy with the rescue efforts.
The sunken ship is about 3 kilometers (1.9 miles) from the shore, where the river is around 15 meters (50 feet) deep, China's state-run broadcaster CCTV reported.
More than 3,000 rescue workers, including 2,100 soldiers, policemen and more than 1,000 civilians were involved in the salvage operation along with approximately 150 boats, the China Daily reported. But the rescue efforts are hampered by strong winds and heavy rain. Seven people swam to shore to alert the police at the time of the incident, it said.
The cruise ship is one of five luxury vessels operated by the state-owned Chongqing Wanzhou Dongfang Shipping Company. The vessel is 76 meters long (249 feet) and has been in service for nearly 20 years with the capacity for 534 passengers, the China Daily said.
According to the World Wildlife Fund, the Yangtze River is the world's third longest river, running for 3,900 miles from the vast Tibetan Plateau to the estuary of the East China Sea near Shanghai.
It says the Yangtze River Basin covers nearly 448 million acres -- more than four times the size of California. Large scale economic growth, industrial and domestic developments have caused the river to become increasingly polluted over the years.
This also isn't the first time that lives have been lost in the Yangtze River. In January, at least 21 people died after a survey tugboat sank on the lower reaches of the river.
A local travel agency has published an emergency call number: +86 13983654321.
The Yangtze River navigation administration telephone number is: +86 (0) 27 82418021.
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