The Yangtze River accident is possibly one of the worst tornado-related disasters in modern Chinese history. The Dongfangzhixing, or Eastern Star, carrying more than 450 people, capsized during a powerful storm in Hubei province on Monday night. A rare tornado occurred in the vicinity of the accident during the storm, the National Meteorological Information Centre said. Radar data analyses show wind speed exceeded 117km/h at the time - enough to generate waves higher than 14 metres. It remains unclear if the tornado caused the accident. And if it did, whether it hit the ship directly, or caused it to change course suddenly. GPS data shows the vessel may have made a sudden U-turn before it capsized. The triple-decked ship - whose draft, or the part below the waterline, measures just 2.5 metres - is susceptible to losing its balance in sudden manoeuvres. One theory is the vessel could have tried to steer from its course to avoid the tornado, but lost its balance in doing so. Watch: Authrorities continue the search and rescue mission for surviving passengers Its high centre of gravity - the result of a poor ratio between the parts of the ship under and above the water - is a common problem for modern cruise ships. Experts have blamed such top-heavy design for Italy's Costa Concordia disaster in 2012. Mainland news outlet Caixin, citing industry insiders, reported that the Eastern Star had been repeatedly modified by people other than its builder. Some question if a direct hit from a tornado can indeed topple a ship more than 70 metres long. Scientists say that while extremely rare, it is not implausible. "To get hit on a river by a tornado is like getting run over by a car on a sidewalk. The chance is very small," said wind engineering scientist Quan Yong, of Shanghai's Tongji University. Infographic - Click to enlarge Tornados are rare on the mainland. Only 97 tornado accidents that caused casualties or financial damage were recorded from 1949 to 1990. There were on average less than three hits a year. "The accident shows how vulnerable humans are in the face of nature," Quan said. Professor Cai Wei, a ship design researcher with the Wuhan University of Technology, said the section of the Yangtze River where the accident occurred was an "A-level navigation zone". This meant the maximum expected height of waves within the zone was up to 2.5 metres. "All ships are built to return to their normal position after facing winds and waves, but if the wind speed exceeds its design limit, the ship will capsize," Cai said. Mainland authorities have yet to conclude the cause of the accident, as it deals with growing concern as to why the ship was allowed to leave the harbour during the storm.