The State Bureau of Investigation obtained a search warrant for user information and content for 15 Instagram accounts in its probe of nude photos of students in Wake County.
Court papers show the SBI wanted to find out who signed up as followers of the accounts.
The SBI has investigated reported of nude student photos on Instagram accounts in nine North Carolina counties. An agency spokeswoman said Monday that four more counties have become involved in recent week.
Almost 70 nude and sexual images of local high school students were exposed to thousands of people Feb. 11.
Special Agent Kevin G. Roughton said in the warrant application that information connected to the accounts could help in bringing charges of second-degree sexual exploitation of a minor and cyberbullying.
The original investigation in Wake County later expanded to Pitt, Craven, Edgecombe, Randolph, Surry, Chatham, Johnston and Durham counties.