The chemical was found in tests carried out following the recall of products made at its Beijing plant, in the latest fallout from the toxic milk scandal which has killed four Chinese infants and made 53,000 others there ill.
"The tests have shown there were traces of melamine," said Tony Bilsborough, a spokesman at the firm's headquarters in Birmingham, central England. He gave no more details and referred questions to the sweet maker's Singapore office.
Cadbury had earlier said it ordered a recall of China-made chocolates in Hong Kong, Taiwan and Australia after internal tests "cast doubt" on the safety of some chocolates, it said in a statement.
The 11 products recalled include Cadbury Eclairs and bulk packets of Dairy Milk chocolate, the company said earlier.
They are the latest in a list, expanding by the day, of China-made foods and drinks that have been removed from stores around the world since the scandal was first exposed earlier this month.
More than a dozen Asian and African countries, plus the 27-member European Union, have taken steps to ban or otherwise limit consumption of Chinese milk-product imports.
Laos and Mali on Monday became the latest to order such measures.
The crisis is among the most serious in a litany of product-safety scandals emerging from China's chaotic and corrupt manufacturing industries in recent years.
Besides the toll in mainland China, five children in Hong Kong, one in Macau, and four people in Taiwan have reportedly developed kidney stones after drinking tainted Chinese products.
Chinese premier Wen Jiabao vowed over the weekend to work to restore his country's reputation, saying it was facing the problem "candidly".
However, a Chinese human rights group said Monday the government was suppressing media coverage vital to assigning blame and preventing a recurrence.
"China has tightened its grip on media freedom to contain rising nationwide outrage at tainted milk products," China Human Rights Defenders, a network of domestic and foreign human rights activists, said in an emailed report.
It cited several instances of reporting by Chinese media censored or banned by authorities. AFP could not immediately verify the allegations.
Normally used in making plastics and fertiliser, melamine is believed to have been added to milk to give it the appearance of higher protein content.
The rights group said the central government had ordered all Chinese media to toe the official line on the issue, thereby preventing exposure of "deep-seated problems in the system."
Xinhua reported last week that officials at Sanlu Group, the dairy firm at the centre of the scandal, knew as far back as December that babies were falling ill but did not report the problem to local authorities until August.
The report, citing a cabinet investigation, said those local officials then waited one month to pass the concerns onto higher authorities.
Police in northern China have detained 22 people in raids on a ring that made and sold the industrial chemical melamine and added it to milk, Xinhua said.
Nineteen of those detained in Hebei province were managers of "pastures, breeding farms and milk purchasing stations," the news agency reported.
The detentions came after more than 800 police raided 41 "pastures, breeding farms, and milk purchasing stations" in and around the city of Shijiazhuang.
Shijiazhuang is the headquarters of Sanlu.