RIO DE JANEIRO (AP) — Brazilian police have arrested five teenagers on suspicion of gang-raping a 13-year-old girl on multiple occasions at a Rio de Janeiro public school.

Police say the girl's boyfriend is among those arrested Monday. They are also investigating the possible participation of several other boys in the four alleged assaults between May and June. The investigation began after a friend recently alerted police.

Investigator Bruno Cleuder tells The Associated Press that police are also looking into whether the school's director may have known about the alleged attacks and failed to take action.

The issue of gang rape became a national topic in Brazil last year after a 16-year-old was allegedly sexually assaulted by gang members who posted videos of the incident on social media.