A Chinese man has been sentenced to life imprisonment for poisoning frozen dumplings which left four Chinese and nine Japanese citizens sick in 2007 and 2008.

Lü Yueting, 39, a former worker at a Shijiazhuang-based food plant, was found guilty of the crime of spreading dangerous substances, the Shijiazhuang Intermediate People's Court in Hebei Province said.

Lü snuck into the refrigeration storehouse of the Tianyang Food Plant three times between October and December 2007, and injected six to nine boxes of frozen dumplings with insecticide because he was unsatisfied with his salary, the Xinhua News Agency reported. 

He attempted to create an incident to attract the attention of managers in order to boost his salary, according to the court.

The contaminated dumplings were sold to Japan and Chengde in Hebei Province. In January 2008, Japanese media reported that 10 people fell ill after consuming frozen meat dumplings produced by the plant.

The plant soon recalled its products and suspended production, resulting in a loss of more than 5.5 million yuan ($908,000). The plant was investigated by both Chinese and Japanese authorities, but no problems were found.

In March 2010, Lü was detained by Chinese police.

The Shijiazhuang Intermediate People's Court held a trial on July 30, 2013, when Lü confessed to the crime in court and apologized to the people who became sick.

It is not clear whether Lü plans to appeal, Li Shiqing, Lü's lawyer, told the Global Times on Monday, adding that he will visit Lü and discuss the appeal in a few days. "I think the verdict is in accordance with Chinese criminal law. Although this case has attracted International attention, it was still a normal criminal case and I hope it will not be overhyped," Li said.

According to China's criminal law, the crime of spreading dangerous substances can receive the death penalty.

The scandal severely damaged the reputation of Chinese food among Japanese consumers and even impacted China's image, Xinhua reported in 2009. 

The verdict was delivered in a public hearing with the presence of journalists and officials from the Japanese Embassy in Beijing.

Xinhua contributed to this story