I would dare to suspect to point out a probable cause: kites.
Kites, also called "pipas" by the local community is a kind of a "national kids sport" in Brasil.
Last time I flew to Brasil I have made an ASR due to a near-miss on final approach to SBRF Rwy 18 and have reported also to TWR.
Kites are a great game sport for kids (and adults), but present a potential danger to aviation when practiced near airports.