RESCUE workers were cutting into the upturned hull of the cruise ship Eastern Star yesterday in an escalated effort to find survivors from the more than 400 people believed to be trapped inside.

The disaster on the Yangtze River could become China’s deadliest shipping accident in almost seven decades. Over 450 people were on board the ship when it capsized on Monday night after being hit by a violent storm in Jianli, Hubei Province.

Rescuers have found only 14 survivors, and so far have retrieved 29 bodies, leaving over 400 people still unaccounted for.

The captain and chief engineer were among the survivors. They are being questioned by police.

Rescuers were planning to cut a 55-60cm rectangular hole on the bottom of the upturned ship to give divers better access to the hull, the rescue headquarters at the site told Xinhua news agency.

“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, “and that means there could still be survivors.”

The major task is how to hold the vessel steady to prevent it from sinking further during the operation. The escape of any air trapped in the hull could cause the ship to lose the buoyancy it has and sink deeper into the water, he said.

Li said divers had managed to attach steel cables to the hull and the plan is to support the ship with cranes while rescuers search inside.

The engineering expert warned over the inevitable thinning of air in an enclosed space over time where people are breathing, adding that “the longer it takes, the less likely we are able to find survivors.”

“We are racing against time, but we are never going to give up,” he said.

State television CCTV showed rescuers, some standing gingerly on the upturned hull, and scores of divers who had worked through the night.

The rescue effort has not slackened off, even though the about 200 divers face difficulties such as cabin doors blocked by tables and beds.

“Although there’s lots of work to do, saving people is still being put first,” transport ministry spokesman Xu Chengguang told reporters.

CCTV showed a rain-soaked Premier Li Keqiang, who is at the scene overseeing rescue efforts, bowing in respect to two bodies laid out on the deck of a boat covered in sheets.

“Life is greater than the heavens, and the burden on your shoulders is massive,” Li told a group of military divers yesterday.

The search area has been expanded up to 220 kilometers downstream, CCTV said, suggesting that bodies could have been swept far away from where the ship foundered in the rain-swollen river.

Three bodies were found 50 kilometers away near Yueyang in neighboring Hunan Province, according to media reports.

Zou Luwang, who lives in a village near the river, said the government called residents to warn of extreme weather on the night the ship capsized. “I believe those who operate the boats have expertise about this, but the weather was unusually bad for these parts,” he told Reuters.

China’s weather bureau said a tornado buffeted the area where the ship was cruising, a freak occurrence in a country where twisters can happen but are uncommon.

The ship overturned “within one or two minutes,” Xinhua quoted the captain as saying. He was dragged out of the water near a pier just before midnight on Monday.

“The river ships tend to have a lower standard on wind-resistance and wave-resistance than ocean ships,” Zhong Shoudao, president of the Chongqing Boat Design Institute, said at a news conference along with weather and transport ministry officials.

“Under the special circumstance of a cyclone, the pressure on the one side of the boat went beyond the standard it was designed for, resulting in the overturning of the boat,” Zhong told The Associated Press.

“The boat had lifejackets and lifeboats, but due to the sudden capsizing, there was not enough time for people to put on lifejackets or for the signals to be sent out,” Zhong said.

The rescue and salvage efforts are being run from a massive barge tethered a few kilometers upstream of the wreckage.

Reached through a watery wasteland of flooded crops and trees torn in half by high winds, it was a bustle of activity, as rescuers, paramilitary troops and army and navy specialists arrived and left by smaller boat.

Access to the site was blocked by police and paramilitary troops stationed along the Yangtze embankment, AP said.

Scores of trucks belonging to the People’s Armed Police were parked along the edge and at least two ambulances were seen leaving the area with their lights on and sirens blaring.

Huang Delong, a deckhand on a car ferry crossing the Yangtze nearby, said he was working on Monday evening when the weather turned nasty.

“From about 9pm it began raining extremely hard, then the cyclone hit and the wind was really terrifying,” Huang said.

The ship was on an 11-day voyage upstream from the eastern city of Nanjing to Chongqing.

While the People’s Daily newspaper said that the ship passed inspections by authorities in Chongqing last month, in 2013 it was investigated and held by authorities due to defects, according to documents from a local maritime watchdog.

The Nanjing Maritime Safety Administration investigated the Eastern Star as part of a safety campaign into passenger ferries and tour boats and held the ship along with five other vessels, according to three documents on the bureau’s website.

The documents did not give details on the nature of the defects but said the issues were reported to the Chongqing maritime safety bureau.

The Eastern Star is owned by the Chongqing Eastern Shipping Corp, which focuses on tourism routes in the popular Three Gorges river canyon region.

China’s deadliest maritime disaster in recent decades was when the Dashun ferry caught fire and capsized off Shandong Province in November 1999, killing about 280.

The Eastern Star disaster could become China’s deadliest since the sinking of the SS Kiangya off Shanghai in 1948, which killed more than 1,000 people.

Condolences came from the UN, United States, European Union and the Vatican. UN Secretary-General Ban Ki-moon said he was “deeply saddened” to learn of the major loss of life as a result of the passenger ship accident.

“The Secretary-General extends his condolences to the families of the victims and also sends his deep sympathies to the government and people of China. He fervently hopes more survivors will be found,” said his spokesman.