PARIS (AP) -- French police demanded that male students and staff at a high school in western France -- 527 people in total -- give DNA samples as they searched for the assailant who raped a teenage girl. The DNA dragnet started Monday in La Rochelle, and prosecutor Isabelle Pagenelle said so far no one had refused. She had warned that anyone who decided not to give a DNA sample would be considered a suspect and could be taken into custody. The testing of male students, faculty and staff at Fenelon-Notre Dame high school is expected to last through Wednesday. Pagenelle said investigators had exhausted all other leads in the Sept. 30 rape of the girl in a dark bathroom at the school. "The choice is simple for me," she said. "Either I file it away and wait for a match in what could be several years, or I go looking for the match myself." Police recovered genetic material from the girl's clothing but had no matches to it in the country's DNA database. France has an extensive DNA database, with a total of 2 million profiles on file as of 2012 -- about 3 percent of the population. "This happened during the school day in a confined space," Chantal Devaux, the private Roman Catholic school's director, told French media. "The decision to take such a large sample was made because it was the only way to advance the investigation." Summonses went out last week to 475 teenage students, 31 teachers and 21 others -- either staff or males who were on campus at the time. Pagenelle's office, which required parental permission for minors, says it will discard any DNA results from people who were eliminated as suspects. Devaux acknowledged that all the results could still come back negative, sending investigators back to the drawing board. "We think there is a strong probability that it's someone from inside, or at least someone who knows the building very well," Pagenelle said.