Circumstances surrounding the 47-year-old Stow man found drowned in Lake Boon on Saturday do not appear to be suspicious, according to the Middlesex District Attorney’s Office. Authorities are not releasing the man’s name, and the investigation is ongoing, according to Stephanie Guyotte, a spokeswoman for the district attorney’s office. The man went missing around 11 p.m. Friday and was believed to be in Lake Boon, State Police said in a previous statement. Upon arrival at the lake, Stow police found a sandal believed to belong to the man. The State Police Dive Team located the man’s body around 5 p.m. Saturday, shortly after they began a search of Lake Boon, which lies partly in Stow and partly in Hudson. The body was transported to the office of the Chief Medical Examiner in Boston.