Paris Brown, 17, had her mobile phone seized and was interviewed under caution by Special Branch investigating the material, they said.
The teenager was forced to stand down from her £15,000-a-year-role as Kent Police's youth police and crime commissioner earlier this month following publication of the tweets.
Today it emerged that Paris's lawyers, Olswang, have written to Kent Police Chief Constable Ian Learmonth about the scope and nature of the investigation, including the decision to seize her phone and for Special Branch to quiz her.
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Rain clearing east tonight for a dry but fresher day tomorrow with plenty of sunny spells.
Heavy rain clearing east for a dry but fresher day tomorrow with some hazy sunshine.
Rain becoming heavy at times this afternoon before clearing tonight. Dry with hazy sunshine tomorrow but feeling fresher.