BEIJING, China (AP) -- An additional 31 batches of Chinese milk powder were found contaminated with the industrial chemical melamine, China's government said Wednesday, further broadening a scandal affecting products ranging from baby formula to chocolate.

The contamination has been blamed for the deaths of four children and kidney ailments among 54,000 others. More than 13,000 children have been hospitalized and 27 people arrested in connection with the tainting.

The new figure, seen on the food safety administration's Web site, brings to at least 100 the number of tested batches of milk powder found to contain melamine.

A previous round of testing, results of which were posted on September 16, found melamine in 69 milk powder batches. Dozens of brands sold by more than a score of dairy firms, including some of China's biggest names, have been among those tested.

Tests have also found melamine in 24 batches of liquid milk produced by three of the country's best known dairy firms.

It was a national holiday in China and product safety officials could not be reached for comment.

The Web site quoted the State Administration of Quality Supervision, Inspection and Quarantine as saying it had tested 265 batches produced by 154 different companies prior to September 14. China has a total of 290 companies making powdered milk, the administration said.

In the most recent tests, nine of the batches containing melamine were produced by the company at the center of the scandal, Sanlu, a 43 percent stake of which is owned by New Zealand dairy cooperative Fonterra. No date for the testing was given.

Melamine, which is high in nitrogen, is used to make plastics and fertilizers and experts say some amount of the chemical may be transferred from the environment during food processing.

But in China's case, suppliers trying to boost output are believed to have diluted their milk, adding melamine because its nitrogen content can fool tests aimed at verifying protein content.

Melamine can cause kidney stones, leading to kidney failure. Infants are particularly vulnerable.

Levels of melamine discovered in batches tested varied widely, from as much as 6,196 milligrams per kilogram to as little 1.3 milligrams per kilogram. Chinese health officials have said no harm comes from consuming less than 0.63 milligrams per kilogram.

The scandal was worsened by an apparent cover-up by companies involved and the ignoring by safety officials of tips and warnings from parents and doctors. Top Sanlu executives and government officials in the northern city of Shijiazhuang, where the company is based, have been forced to resign.

Also on Wednesday, Hong Kong's food safety agency said its tests have found melamine in a Japanese brand's Chinese-made cheesecake.

The Centre for Food Safety said a sample of Lotte Cream Cheese Cake manufactured by Japan's Lotte China Foods Co. Ltd in mainland China was found to contain melamine.

Hong Kong and Macau authorities earlier detected excessive melamine in Lotte's popular Koala's March chocolate and strawberry cream cookies.