Canals near Olympic Park have been invaded with tonnes of weeds

Canals surrounding the Olympic Park have been invaded by a green carpet of duck weed - near the World Championship which has been marred with outbreaks of gastroenteritis. Teams are collecting up to 120 tonnes of green sludge every week on two canals in the capital as it multiplies in the heat. Athletes staying in the capital for the World Championships have contracted gastroenteritis, leading to many withdrawing from Monday's heats. An individual piece of duck weed is no bigger than a ladybird, but they reproduce rapidly and together can resemble a thick carpet across the water.