Five people have died and hundreds are missing after a cruise ship carrying 458 people capsized on the Yangtze River in China's Hubei province.
Officials say at least 14 people survived, with some found alive inside the submerged hull of the Eastern Star.
The captain and the chief engineer, who both survived, have been detained. They say the boat was caught in a cyclone.
The boat sent no emergency signal, with the alarm reportedly raised by those who had swum to shore.
Other reports said the crew of another vessel alerted the authorities after rescuing the captain from the water.
Chinese media quoted the captain as saying the vessel sank within minutes, while many people were asleep. weather forecaster Peter Gibbs says severe thunderstorms in the area may have caused the ship to capsize.
Most of those on board were tourists aged between 50 and 80 who were travelling from the eastern city of Nanjing to Chongqing in the south-west - a journey of at least 1,500km (930 miles).
The ship sank in the Damazhou waterway section of the Yangtze, where the world's third longest river reaches depths of about 15m (50ft).
At least 14 people have so far been rescued and some with minor injuries have been taken to hospital, officials told reporters. Three of them were rescued from inside the upside-down hull of the ship after it was cut open, Xinhua reports.
Strong winds and heavy rain have been hampering the rescue efforts. According to the People's Daily, three bodies were recovered in Yueyang, Hunan province, some 50km away from the site of the sinking.
Could weather front be behind Yangtze sinking?
The BBC's Jo Floto in Beijing says that China has not seen a disaster on such a scale for a long time.
More than 50 boats and 3,000 soldiers and emergency personnel are involved in the rescue efforts, with more than 100 divers also sent to the site.
Local media said the rescue attempt had been hampered by rainy weather
Up to 1,000 policemen have reportedly joined the rescue operations
Footage aired on state TV showed divers knocking on the submerged hull with hammers to try to make contact with people believed to be trapped below.
Chinese premier Li Keqiang has arrived at the scene, according to the People's Daily.
Eastern Star - Dongfangzhixing in Chinese - had been carrying 406 Chinese passengers, five travel agency employees and 47 crew members.
The 76m-long ship weighs 2,200 tons, and could accommodate a maximum of 534 people.
The boat went down in a popular cruise area of the river
The boat sank at about 21:30 local time on Monday evening (13:30 GMT), but rescuers did not reach the vessel until at least two and a half hours later.
CCTV said the vessel was owned by the Chongqing Eastern Shipping Corporation which runs tours to the scenic Three Gorges river canyon area along the Yangtze River.