A map of China made from more than 1,800 cans of baby formula created by dissident Chinese artist Ai Weiwei went on show in Hong Kong Friday, reflecting the controversy over mainland demand for milk powder. A surge in demand for formula in China sparked by fears over the safety of domestic milk powder has seen shop shelves around the world cleared out by Chinese buyers and unofficial exporters. The Ai Weiwei exhibit entitled 'Baby Formula 2013' uses 1,815 full cans of seven brands of milk powder and covers a 10-metre by 8-metre floor space. "The piece is related to several problems," Ai Weiwei told AFP on Friday. "One is the recent ban on mainland residents buying milk powder and bringing it back to China, and then there is the issue of why Chinese mainlanders go to Hong Kong to buy milk powder." In Hong Kong, anger about visitor purchases saw the city ban travellers taking out more than 1.8 kilograms of formula from March 1 this year. Banners at the border warn of HK$500,000 (US$64,000) fines and two-year jail sentences for offenders. Demand from the mainland is driven by memories of a 2008 scandal over Chinese formula tainted with the industrial chemical melamine which killed six children and affected more than 300,000 others. Distrust grew last year when another domestic manufacturer's formula was found to be contaminated with carcinogens, despite official pledges to clean up the industry. "We know that on the mainland food safety is a very serious problem. It largely related to a lack of supervision and moral decay within industry," said Ai. "Hong Kong people make profits from these problems, and are also victims," he added. Executive director of the Para Site art space Cosmin Costinas, which is hosting the installation as part of a wider exhibition and has collaborated with Ai in the past, told AFP that all the cans of milk powder in the exhibit had been bought in Hong Kong. There will be no extra security to stop them being stolen, he said. In Australia, Chinese customers have been blamed for a shortage of formula in supermarkets and pharmacies, causing some outlets to ration sales, with limits also imposed in Europe after a run on baby milk powder. China is "by far" the world's largest market for formula, says consumer research group Euromonitor. Breastfeeding rates are low -- just 28 percent according to a 2012 UNICEF report -- due to time limits on maternity leave and aggressive marketing of formula.