Charles Oliver, 44, is charged with assaulting the five women at his home in Woodstock, Ill., from November 2011 through early 2013.
Woodstock police said a search of Oliver's home turned up women's personal items that don't belong to the alleged victims already identified. Police said they found cellphones, copies of women's driver's licenses and identification cards, the Chicago Tribune reported.
McHenry County Assistant State's Attorney Sharyl Eisenstein said investigators found thousands of images and videos of women involved in sexual acts with Oliver.
"Some appear consensual but many appear forced," she said.
Police allege Oliver met the women through personal ads posted on the Craigslist website.
He would allegedly meet them elsewhere and take them to his home.
One woman said she was locked in the basement, while another said he tied her to a chair.
Oliver was free on bail after being arrested Jan. 28 for assaulting two women when he was arrested Feb. 24 and charged with attacking three more women.
Prosecutors sought to have his bail revoked while he awaits trial but the judge denied the request, setting bond at $3 million, the newspaper reported.