An estimated 11,000 boats are now stuck on a stretch of the historic Grand Canal in eastern Jiangsu province after flooding on nearby lakes forced authorities to close the waterway, officials and state media said. Officials estimate about 4,000 boats, mainly small cargo vessels, are waiting around the cities of Huaiyin and Huaian, while a further 7,000 are gathered near Yangzhou city. Flooding earlier this month on the Huai river and Shaobo lake had caused authorities to order a halt to shipping on the canal until water levels had fallen and currents had slowed, officials said. The boats have been piling up ever since. Officials said that traffic could resume once the waters had receded. That could take from 10 days to two weeks, the China Daily newspaper said. Some boats carrying flood relief supplies to nearby Anhui province, where flooding on the Huai river was the most serious, claiming 17 lives, were allowed to make the journey despite the danger, officials said. With most boats motionless, the main concern of local officials is supplying the crews with food and fresh water and preventing outbreaks of disease. An official working for the canal's northern Jiangsu management office said that authorities were supplying the crews with daily necessities and disinfecting the boats. Most of the boats were carrying cargo such as coal and sand, and not perishable food, he said. Some boat operators were angry about the potential loss to their business, but officials described the mood as stable. The Grand Canal stretches between Hangzhou and Beijing, but less than half is still navigable. Workers built most of the canal from 605 to 609, during the Sui dynasty. Few passenger boats still use the canal, although it has proved to be a tourist attraction.