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.
More top news
The NSPCC has revealed that it dealt with nearly 19,500 calls and emails from concerned adults in the last year relating to child neglect.
Nearly 500 identity frauds were reported every day in the first half of this year.
Amanda Houston has Wednesday's forecast for the east of the ITV Meridian region.