State media said Monday authorities in China are hunting for nearly 100 tonnes of melamine-laced milk powder left over from 2008, when six babies died from consuming the toxic substance.

According to AFP, the discovery came as authorities pursue a crackdown on dairy products that should have been destroyed after the melamine scandal but have been illegally resold -- reviving concerns about food safety and inspection standards.

The China Daily said two dairy firms in the northern Ningxia region were closed down Saturday for selling tainted milk powder, and candies made with contaminated powder were found in the northeastern province of Jilin.

The report said Police in Ningxia found that a company outside the region gave one of the dairy firms around 170 tonnes of tainted milk powder left over from the 2008 scandal as debt payment in July last year.

The firm involved -- the Ningxia Tiantian Dairy company -- then repackaged nearly all of the powder and sold it to five factories in provinces and regions in northern and southern China, the report added.

Only 72 tonnes of powder have been recovered and authorities are tracking down the rest.

It was unclear whether the dairy firm knew the product was contaminated.