Oklahoma City Police Chief Bill Citty said at a news conference that Holtzclaw stopped women while he was working and forced them to expose themselves, fondled them and in at least one instance had intercourse with a woman.
Authorities have statements from six victims and expect a statement from a seventh, Citty said. He also said investigators believe there are additional victims.
The department began investigating Holtzclaw after a woman complained to police June 18, the chief said. Holtzclaw was placed on leave that day.
"We started the investigation and we started looking at traffic stops he had made throughout the previous months to try to identify and initiate contact with females that we knew he had stopped during that period of time ... to see if they had been sexually assaulted," Citty said.
Records indicate Holtzclaw is in custody at the Oklahoma County Jail. The records don't list an attorney, and jail staff said they could not provide attorney information.
Oklahoma County District Attorney David Prater, who also attended the news conference, said he anticipates charges against Holtzclaw will be filed by Aug. 29.