BEIJING, March 28 (Kyodo) —

A suspect caught in the poison dumpling case, which caused anxiety in Japan over the safety of foods imported from China, has admitted during questioning earlier this month that he tainted the food with pesticide, the Ministry of Public Security said Sunday.

The suspect identified as Lu Yueting, a former temporary employee at the Tianyang Food Plant in Hebei Province, stole methamidophos from the factory in the summer of 2007 and later used a syringe to inject the substance into the frozen dumplings on three occasions, a senior ministry official told Japanese media organizations, including Kyodo News.

Officials at the plant, located in the northern city of Shijiazhuang, had said earlier that there is no pesticide at the factory.

The questioning began March 16 and the syringe was found five days later in a sewage line at the factory, the ministry official said, adding that Lu was dissatisfied with the gap between his pay and the salaries of the factory's regular workers, which was the apparent motive.

The official also said investigators had focused their attention on Lu throughout the probe leading up to the questioning, which came after the suspect told his wife and relatives that he committed the crime.

On Friday, China said it had detained the 36-year-old man suspected of being involved in the case. The pesticide-tainted dumplings caused 10 people to fall ill in Japan about two years ago, prompting Tokyo to urge China to investigate and resolve the issue as soon as possible.

Speaking to reporters in Shijiazhuang, the suspect's 66-year-old father expressed bewilderment at his son's actions. He added the suspect was "a quiet boy who didn't say a lot."