GRAND RAPIDS — The Federal Bureau of Investigation found at least 37,000 images and videos of child pornography on hard drives seized during a search of Larry Nassar's Holt property, as well as videos that show the former Michigan State University doctor sexually assaulting girls under the age of 12, an agent testified today in federal court in Grand Rapids.

The hard drives were found in a garbage can on Nassar's property while law enforcement executed a search warrant, special agent Rod Charles testified during a detention hearing for Nassar.

►Related: At MSU: Assault, harassment and secrecy

Nassar, 53, is charged with two child pornography counts in federal court. His indictment was unsealed last week. It said that, during a nearly 14-year stretch, Nassar collected "thousands of images of child pornography" including those of someone younger than 12.

►Related: MSU, Nassar sued for sexual abuse

Nassar was in court Wednesday afternoon for a series of hearings, which included a formal arraignment and pretrial conference. He wore jeans, a red long-sleeved fleece sweatshirt and glasses. He was led into the courtroom by two federal agents with his hands cuffed behind his back.

Federal Magistrate Judge Ray Kent ordered that Nassar remain detained without bond, saying he was the "worst" kind of danger to the community. Kent characterized the evidence as "very heavy against Dr. Nassar."

Charles testified that, when Nassar turned in a work laptop to Michigan State University, its hard drive had been wiped clean.

In a statement released Monday, MSU Spokesman Jason Cody said, "The current (federal) charges do not relate to Nassar’s employment at MSU. Also, according to MSU Police, the investigation into the child pornography charges has not revealed any images of victims in the complaints of criminal sexual conduct that the department also is investigating."

Matt Newburg, Nassar's attorney, said his client knew about criminal investigations as early as August and has cooperated with police. He asked Kent to order Nassar to be detained in his Holt home and on a GPS monitor.

Trash collection was running late the day of the search warrant, Charles testified, and an officer checked the garbage bin by the curb. The officer found several external hard drives, some that had Nassar's name or phone number written on them, Charles testified.

The FBI recovered videos that showed Nassar sexually assaulting young girls in a pool, Charles said.

Charles testified that the FBI continues to conduct forensic reviews of computers collected from Nassar, some of which appear to have had their hard drives cleared. He added that the child pornography included photographs of young girls exposing themselves as well as videos of young girls being raped.

In asking for Nassar to remain detained, Sean Lewis, assistant U.S. attorney, said Nassar was "a hands-on offender in any context he can put himself into." He emphasized to Kent that some of the sexual assault allegations date back decades. He emphasized the ages of the alleged victims, which include one as young as 6.

"If true, that's appalling," Kent said. "And I'm not going to set Dr. Nassar loose in our community until this (case) is resolved."

Nassar was charged last month in Ingham County with three counts of first-degree criminal sexual conduct involving a person younger than 13. He had been free on $1 million bond.

Nassar faces five to 40 years in prison, and up to lifetime supervision upon release, if convicted on the federal charges. He faces up to life in prison if convicted on the Ingham County charges.

State and local law enforcement officials have said about 50 women have come forward since this summer with allegations that Nassar sexually assaulted them, some saying it occurred during medical procedures. The wave of allegations came after the Indianapolis Star detailed sexual assault allegations against Nassar by two women.

During the hearing Wednesday, Charles, the FBI agent, estimated the number of women who have come forward with allegations could now be closer to 60.

Newburg said Children's Protective Services investigated Nassar recently and that his children made no claims of sexual misconduct.

The former MSU team physician, who was fired in September, served as USA Gymnastics’ team physician during four Olympic Games and is one of the figures in a nationwide scandal involving how the organization handles allegations of sexual assault.

The university and its police department investigated Nassar in 2014 after a then recent graduate alleged that Nassar sexually assaulted her during a visit to his campus office for a treatment for hip pain. The university's Title IX investigator cleared Nassar and the Ingham County Prosecuting Attorney's Office declined to issue charges.

Officials have said both cases have been reopened.

Charles testified that a teen girl has alleged that Nassar sexually assaulted her during medical appointments between the fall of 2015 and earlier this year.

At MSU: Assault, harassment and secrecy

ContactMatt Mencarini at (517) 267-1347 or mmencarini@lsj.com. Follow him on Twitter@MattMencarini.