The U.S. Department of Justice on Monday announced it was investigating how rape cases in Missoula, Montana were being handled by local authorities.

Assistant Attorney General for the Civil Rights Division Thomas E. Perez said there was “serious concern” that as many as 80 rape cases “were not being investigated in a prompt and adequate fashion.”

A number of those cases involved students at the University of Montana. In December 2010, two female students were allegedly gang-raped by several male students of the Grizzlies football team. The case lay dormant for a year, until a similar incident occurred again in December 2011.

The university hired former Montana Supreme Court Justice Diane Barz to investigate the sexual assaults. After the investigation grew to include nine more victims, she concluded that “UM has a problem of sexual assault on and off campus.”

The U.S. Department of Justice will conduct a civil investigation of the university’s policies and practices regarding sex crimes.