A woman received a lethal injection on Tuesday for lacing milk with nitrite which killed three children and sickened more than 30 others in Northwest China, a local court said Wednesday.

Ma Xiuling and her husband Wu Guangquan, two dairy farmers from Pingliang City, Gansu Province, deliberately added nitrite, an industrial salt, to fresh milk produced by a business rival in April 2011, according to a statement from the Pingliang Municipal Intermediate People's Court.

Ma and Wu committed the act against their competitor, another couple, after several business disputes, it said.

A one-month-old baby and two children under two died after drinking the poisonous milk.

In November 2011, Ma was sentenced to death by the Pingliang court for intentionally poisoning milk and Wu was given life in prison for purchasing the poison.

In June 2012, the Gansu Provincial High People's Court upheld the verdict after the couple appealed.