In this photo released by China's Xinhua News Agency, a nurse takes care of sickened child at Hebei People's Hospital in Shijiazhuang, 16 Sep 2008

Chinese authorities say four infants have now died after drinking contaminated milk powder that has sickened more than 6,000 babies across the country.

Chinese officials announced the latest fatality Thursday, saying it occurred in the remote western region of Xinjiang.

China's health minister says 158 of the country's sick infants are suffering from acute kidney failure.

The milk was found to contain the chemical melamine.  It is believed the manufacturer used the chemical to give watered-down milk the appearance of having high protein levels. 

In the wake of the scandal, China has canceled inspection exemptions given to companies with proven quality records.

Meanwhile, 12 people have been arrested in Hebei province, bringing the total number of arrests to 18.

Hebei is home to the Sanlu Group, the company that produced the tainted formula.  The group's chairwoman, Tian Wenhua, has been dismissed from her post and is being detained by authorities.  The mayor of Shijiazhuang city, where Sanlu is based, has also been fired, along with four other officials.

Six of those arrested allegedly sold the chemical, while the other 12 were suppliers accused of contaminating the milk.

Separately in Hong Kong today, authorities have ordered the recall of dairy products made by China-based Yili Foods after eight out of 30 of its products tested positive for melamine, including milk, yogurt and ice cream. 

China's Health Ministry has pledged free health care to all children sickened by the tainted milk.   The government also has stationed 1400 inspection teams at dairy-producing enterprises across the country.   It has also pledged to increase inspection of all dairy products, as well as imported and exported feed, for the presence of melamine. 

Some information for this report was provided by AFP, AP and Reuters.