PARIS (AP) — French investigators began taking DNA samples Monday from 527 male students and staff at a high school — including boys as young as 14 — as they searched for the assailant who raped a teenage girl on the closed campus.

Testing began Monday at Fenelon-Notre Dame high school in western France. All those who received summonses last week were warned that any refusal could land them in police custody, and no one rejected the sweeping request to test the high school’s male population.