Farrell, a 61-year-old native of Aruba, was found dead Dec. 30 in his hotel room in St. Petersburg, where the group had come for a performance.
Sergei Kaptionov, a spokesman for the St. Petersburg branch of Russia's Investigative Committee, was quoted by Russian news agencies on Wednesday as saying the death was due to heart disease and was not a criminal matter.
Boney M was popular in the 1970s with hits including "Daddy Cool."
