Police are investigating the June death of a 4-month-old boy from Kobe who suffered multiple-organ failure days after receiving a massage from the 56-year-old female director of a nonprofit organization.

The NPO, which was founded in 2003 in the city of Joetsu, Niigata Prefecture, but has branch offices in Osaka and Tokyo, has offered baby massages for years using their own in-house techniques.

The group's director had previously been the subject of another police probe in connection with the death of a baby boy in Niigata Prefecture in February 2013, who died the same day he received her massage.

Following the infant's death, prefectural police sent the case to the Niigata Public Prosecutor's Office, but officials decided not to indict the woman, investigators said. It was not clear why the case was dismissed.

Investigative sources said the woman — who is not publicly licensed — had used her own custom massage techniques on the child from Kobe, claiming that the therapy makes babies healthier and less prone to disease and injury.

"This technique does not carry any risk thus it has no relation to the (Kobe boy's) death," the woman told a reporter on Monday.

The investigators said the condition of the Kobe baby had deteriorated soon after she massaged his body and neck. The cause of the child's death was determined to be brain damage resulting from a lack of oxygen as well as multiple organ failure.

A 71-year-old senior member of the nonprofit organization said that the woman has also promoted her own original baby slings for mothers, and has offered massage therapy training sessions for parents. The man added, however, that since the death of the Kobe boy the woman has limited her work with young children.