A police officer in Aichi Prefecture is suspected of leaking information on last year's massive gold bar theft in Fukuoka to a suspect before 10 people were recently arrested in connection with the case, investigative sources said Friday.

The 10 were arrested in May over the theft of gold bars worth ¥750 million ($6.7 million) last July by men disguised as police officers on a street in the city of Fukuoka.

The sources said Fukuoka police began wiretapping a potential suspect earlier this year based on security camera footage and other information, and overheard the Aichi police officer talking with the suspect.