The towers of Disney's planned Magic Kingdom in Shanghai are wreathed in scaffolding and mystery after the US entertainment giant pushed back the opening of its first mainland China theme park to next year. On a tightly guarded 3.9 sq km site east of the city, a grey turret of the unfinished "Enchanted Storybook Castle" rises skyward. There is no Disney branding at the main entrance, only a sign reading "Shanghai International Tourism and Resort Zone". It was originally due to be transformed in time to open this year, but Disney chairman and chief executive Bob Iger last week announced the opening would be delayed to next spring. He attributed the change to an expansion in the park's size and number of attractions. "The artistry, complexity, the magnitude and the detail, it's all quite astonishing," Iger said, calling the facility "spectacular". But Shanghai authorities have not confirmed any plans to expand the project, and people familiar with it point to it following stricter environmental and labour standards than normal on the mainland. Disney and its Chinese partner, state-backed Shanghai Shendi Group, broke ground on the park in April 2011. Construction on the mainland is normally staggeringly fast, with towering skyscrapers and multi-lane highways changing urban landscapes at a clip. But a Shanghai official said one delay arose after contaminated soil on the site failed to meet environmental standards, prompting Disney to bring in a foreign contractor to remedy the problem. Workers removed topsoil up to a metre deep. A worker said the builders were insisting on a standard eight-hour workday, preventing faster construction - unlike many other sites on the mainland where labour laws are loosely enforced and routinely violated. Disney did not reply to a request for comment on the delay. The Shanghai government is promising to finish a metro line extension linking to the park and other infrastructure this year.