A Hong Kong-led scientific team has discovered a new source of the Yangtze River, adding to the confusion over the origin of Asia's longest river. The new source, a tributary about 12km long named the Duozaoneng, is located on Qinghai's southern border with Tibet . It was discovered by the Hong Kong-based China Exploration and Research Society, headed by president Wong How-man. The discovery supersedes an earlier source identified by Mr Wong 20 years ago. It also casts doubt on the government-sanctioned origin at the Tuotuo River, which rises from the glaciered mountain Geladaindong in southern Qinghai. The site is a popular tourist spot, graced by a monument reading 'Yangtze source' in former president Jiang Zemin's handwriting. Wong, 55, who made two expeditions to define an earlier identified source, the Riashaneng, in 1985 and 1995, said the idea of probing the area again came from a review of the latest high-resolution satellite images of the region last year. 'I found out that I had overlooked a nearby tributary which is more than 1km longer than the old source,' he said. 'This tributary was obscured by clouds when I studied the large-format camera images from the space shuttle in 1981 for my 1985 expedition.' The group found Duozaoneng, at an elevation of 5,170 metres, last month. Like the Riashaneng, the river is also a tributary of the Damqu, but is 1km longer, making it the higher source of flow to the Yangtze. The 19-member team arrived at the southern end of the Duozaoneng on June 15 after a day-long trek by vehicle and horse. The group found the water flow changed dramatically during the day, with little in the morning but with much more volume later on, becoming a big stream by late afternoon, Wong said. Members of the group were analysing findings from the Duozaoneng, the results of which would be released in scientific journals in the coming months. 'I call Tuotuo River the 'official' or 'convenient' source as it is endorsed by the Chinese government as well as being much easier to reach,' Wong said. 'It also has beautiful glacier scenery. 'However, from a scientific perspective I think the origin of a river should be where it stretches the furthest.'