Police says, the accused received orders from the North's Reconnaissance Bureau, to kill Hwang Jang-Yop. Jang-Yop was found died earlier in his bathtub on Oct 10 from heart attack.
According to police, Jang-Yop had suffered heart failure the day before he was planned to be assassinated.
After receiving several death threats Jang-Yop lived under police guard at an undisclosed address in Seoul.
"No traces of any drug or poison were found in his body. There was no foul play involved in his death," the police statement added. We are closing the investigation since there are no grounds to suspect a homicide," police said earlier.
In Jul, two North Korean spies were sentenced to 10 years in prison in Seoul for plotting to murder Hwang.