China promises 'no cover-up' in ship sinking probe as death toll rises to 65

China has pledged that there would be "no cover-up" of an investigation into the sinking of a cruise ship on the Yangtze River, which has left 65 people dead and over 370 missing, as angry families gathered near the rescue site to demand answers.

Authorities are investigating the crew members who were rescued from the Eastern Star, which capsized in a freak tornado on Monday night, and were "gathering evidence", Xu Chengguang, the spokesman for the Ministry of Transport, said.

"We will never shield mistakes and we'll absolutely not cover up (anything)," Xu told a news conference on Wednesday night, adding a preliminary investigation had begun.

Only 14 survivors, including the captain and chief engineer, have been found since the ship carrying 456 people capsized, in what could be China's worst shipping disaster in almost 70 years.

Police have detained the captain and chief engineer for questioning. An initial investigation found the ship was not overloaded and had enough life vests on board.

The announcement of the investigation came hours before dozens of relatives broke through a police cordon in bid to reach the disaster site.

Frustrated by the scarcity of information from local authorities, about 50 family members hired a bus to take them from Nanjing to Jianli county in Hubei, an eight-hour journey.

The ship had been on an 11-day voyage upstream from Nanjing, near Shanghai, to Chongqing.

Relatives have asked the government to release the names of survivors and the dead, and questioned why most of those rescued were crew members. Some have also demanded to know why the boat did not dock in the storm, and why the rescued captain and crew members had time to put on life vests but did not sound any alarm.

On Thursday, there was a heavy security presence outside one of the hotels where some family members were staying.

"Right now the government has an attitude of complete apathy towards us," said Cao Feng, 40, whose parents were on board. "We just want to be closer to our relatives."

June 4 marks the anniversary of the 1989 crackdown on pro-democracy demonstrators around Beijing's Tiananmen Square, and protests are usually quickly halted in China.

Rescuers are not giving up their search of the ship, which was carrying many elderly Chinese tourists, despite the fading hopes of relatives.

They have begun cutting small holes through the Eastern Star's upturned hull to get better access, although no more survivors have been found, state media reported.

"The ship sank in a very short time frame, so there could still be air trapped in the hull," Li Qixiu of the Naval University of Engineering told Xinhua. "That means there could still be survivors."

The search area has been extended up to 220 km (135 miles) downstream, suggesting that bodies could have been swept far from where the ship foundered.

State media said it was the worst recorded ship disaster on the Yangtze River. In 1948, the steamship Kiangya blew up on the Huangpu river, killing more than 1,000 people.