DETROIT (AP) — The U.S. Justice Department says it won’t pursue criminal charges against former FBI agents who failed to quickly open an investigation of sports doctor Larry Nassar.

Agents knew in 2015 that Nassar was accused of sexually assaulting female gymnasts.

Nassar wasn’t arrested until 2016.

The Office of Inspector General found that two former agents likely provided “inaccurate or incomplete information” when investigators subsequently tried to understand what happened. But the Justice Department says more would be needed to file charges.

Nassar was a Michigan State University sports doctor as well as a doctor at USA Gymnastics. He is serving decades in prison for assaulting female athletes and possessing child pornography.