Six Chinese men went on trial Friday, accused of making and selling the chemical at the heart of the tainted-milk scandal.

Among the accused is the owner of an illegal workshop that was allegedly the country's largest source of melamine, state media said.

Melamine contamination in dairy products has been blamed for killing at least six children and making nearly 300,000 others sick.

Police say Zhang Yujun, 40, ran a workshop on the outskirts of Jinan in eastern Shandong province that manufactured and sold a "protein powder" composed mainly of melamine and malt dextrin, the official Xinhua news agency reported.

The powder was added to watered-down milk to make it appear high in protein content.

Prosecutors in the Shijiazhuang Intermediate People's Court accused Zhang of producing more than 700 tonnes of "protein powder" that contained melamine from October 2007 through this August. His workshop was alleged to be the largest source of melamine in the country.

He allegedly sold about 550 tonnes with a total value of $1 million US, the court heard.

In the same case, a second man, Zhang Yanzhang, 24, was accused of buying and reselling the product.

State television showed both men in court in handcuffs with their heads bowed while being questioned by three judges.

Four other men were being tried in three separate courts across Hebei province for adding the chemical to raw milk and then selling it to Sanlu Group Co., the main company in the scandal, according to Xinhua.