SHIJIAZHUANG, China (CNN) -- The former chairwoman of China's Sanlu dairy was sentenced to life in prison and three others received death sentences Thursday in a tainted milk scandal that killed at least six infants and sickened nearly 300,000 others.
Police surround a court building in northern China in late December during the trial.
Tian Wenhua and three other Sanlu Group executives were put on trial for producing and selling fake or substandard products after their arrests in late September.
Tian, who pleaded guilty in December, received a life sentence Thursday. Former deputy general managers Wang Yuliang and Hang Zhiqi received sentences of 15 and eight years, while Wu Jusheng, a former executive heading Sanlu's milk division, was sentenced to five years in prison.
In addition, Sanlu, Tian and Wang were ordered to pay multi-million dollar fines.
The court also sentenced three people to death, including a suspended sentence pending a review, and two others to life in prison. Six more received prison terms of five to 15 years each.
Many of the defendants -- including one who received a death sentence -- were middlemen who sold melamine to milking stations that added the chemical to the milk. Watch more on the sentencings »
Security was tight ahead of the verdicts, as police set up roadblocks a kilometer (0.63 miles) in each direction from the courthouse.
Parents outside the courthouse were outraged by the sentence that spared Tian's life. A mother who's baby died from contaminated milk said she wanted Tian shot to pay for the life of her child.
Twenty-one suspects went on trial late last month. Nine have yet to be sentenced.
Sanlu was one of the main distributors of the tainted milk, which caused kidney stones and urinary tract problems in hundreds of thousands of children.
From early August to mid-September, Sanlu produced 904 metric tons of melamine-tainted baby formula powder and sold 813 metric tons of tainted products made with contaminated milk, the state-run Xinhua news agency reported. Watch how China's dairy industry has been affected by the scandal »
Chinese investigators found melamine in nearly 70 milk products from more than 20 companies, according to quality control official Li Changjiang, who was eventually forced to resign.
The Ministry of Health has said the contamination likely caused the deaths of at least six babies. Another 296,000 infants suffered from urinary problems, such as kidney stones.
The tainted formula came to light in September after babies who were fed milk powder produced by the Sanlu Group, which recently filed for bankruptcy, had developed kidney stones.
Melamine is commonly used in coatings and laminates, wood adhesives, fabric coatings, ceiling tiles and flame retardants. Some Chinese dairy plants added the chemical to milk products so they would appear to have a higher protein level. Learn more about melamine »
Victims of tainted baby formula are expected to be compensated by the 22 Chinese dairy producers that made the milk.
"The enterprises offered to shoulder the compensation liability," the country's Dairy Industry Association said late last month, according to Xinhua.
"By doing so, they hope to earn understanding and forgiveness of the families of the sickened children."
The group said victims will receive a one-time cash payment, but did not provide the amounts, according to Xinhua.
No date for the payments was given. The dairies also raised money to cover medical bills for any after-effects suffered as a result of the poisoning, the association said.