Police suspect the mastermind behind a kidnapping in which six Chinese illegal immigrants have been arrested may still be at large, investigative sources said Feb. 12.

Lin Jianming, 29, and five others were arrested Feb. 11 on suspicion of kidnapping four compatriots and demanding 35 million yen in ransom. The victims were rescued the same day from an apartment in Arakawa Ward, Tokyo. Most of the suspects, as well as the victims, have been identified as undocumented immigrants from China. They are all from Fujian Province, the sources said.

The suspects have told police that 11 people were involved in the abduction. One of the six suspects has told investigators he was lured into the kidnapping plan several days before it took place, the sources said. The alleged mastermind, according to the suspect, is currently in hiding in Japan.

Investigators suspect an underworld syndicate was involved in the case because the amount of ransom the captors demanded is high relative to the average income in China, they said. Investigators are focusing on possible links to the Snakehead smuggling syndicate. The Metropolitan Police Department has launched an investigation into the Snakeheads in connection with a recent surge in the number of Chinese trying to illegally enter Japan by sea. Media reports have said the Snakeheads demand between 2 million yen and 3 million yen from each would-be immigrant if they succeed in entering Japan.