In addition to the arrests, police detained 41 other people and seized 227 tons of milk products contaminated with melamine, the China Daily said Monday.
The six arrested were charged with producing and selling milk containing an excess of the chemical.
Melamine is a synthetic material used in producing plastics such as Formica, and for making concrete. Because of its high nitrogen content it has been used as an adulterate for animal feeds and milk products to increase their apparent protein content.
In a previous crackdown on toxic milk products in 2008, at least six infants died and the additive, up to 500 times the acceptable limit, sickened another 300,000 children.
The latest melamine contaminations were first reported in northwest China's Gansu province in June, the report said.
Investigators said some of the products seized were from the 2008 crackdown. Those milk products were supposed to have been destroyed.
Three executives from the Shanghai Panda Dairy Co. were sentenced to jail terms of up to five years in March for their roles in the 2008 milk contaminations.
Chinese officials in June reduced the required protein level in dairy products from 2.95 percent to 2.8 percent in an effort to discourage farmers from using additives, the report said.