Zhang Yujun and Zhang Yanzhang were accused of involvement in producing a melamine-laced powder that enabled milk to appear higher in protein.

The so-called "protein powder" was then sold to dairies, and led to the deaths of six children and made 300,000 ill. They are the first in several sentences due over the scandal.

One of the most eagerly awaited sentences is that of Tian Wenhua, who was general manager of the Sanlu Group. She has already pleaded guilty to charges of producing and selling fake or substandard produce.

The Sanlu dairy was at the centre of the scandal, in which milk was allegedly watered down in order to make supplies go further and make more money.

They are accused of disguising what they had done by adding powder containing the industrial chemical melamine.

The scandal came to light last September when a number of babies, drinking powdered formula milk, fell ill with kidney stones caused by the melamine.