San Francisco (CNN) A man accused of posing as a rideshare driver and raping several women in San Francisco was living in the country illegally, according to federal immigration authorities.

Last week, San Francisco police arrested Orlando Vilchez Lazo, who faces multiple charges, including false imprisonment, kidnapping, assault with intent to commit rape, sexual penetration with a foreign object and rape.

Vilchez Lazo appeared in court Thursday morning and entered a not guilty plea. He was ordered held without bail.

US Immigration and Customs Enforcement has placed a detainer with the San Francisco County Jail on the suspect, who is a citizen of Peru.

"It's completely premature to be talking about the facts as alleged," Deputy Public Defender Eric Quandt said at his hearing Tuesday, according to CNN affiliate KGO.

"ICE has made this case about sanctuary laws and immigration status, and that has nothing to do with the charges that are being brought by the District Attorney," Quandt said, according to the station.

Police say Vilchez Lazo targeted women outside bars in downtown San Francisco and lured them into his car by posing as a rideshare driver before raping them. He is also accused of using a knife in the attacks, according to the criminal complaint.

"These assaults were not date rapes. They were not acquaintance rapes. These assaults were violent rapes committed by a serial rapist -- a sexual deviant predator who was not going to stop until it was caught," Police Cmdr. Greg McEachern had told reporters.

As police worked the case, they had begun calling the suspect the "Rideshare Rapist."

Vilchez Lazo has been linked to four attacks in the past five years. The first assault was reported in 2013; three others were reported in February, May and June of this year, and police believe there could be more victims. Investigators are asking any victims or anyone with information to contact the San Francisco Police Department and the District Attorney's office.

The four cases followed a similar pattern in which women used a ride share service to leave bars, but were picked up by the suspect claiming to be their driver. They were driven to a secluded location where they were raped in the backseat; some of them were threatened with a knife, according to court documents. All four women went to the hospital to have sexual assault kits collected.

"In all four cases, the defendant separated the victims from their phones and in all four cases he is linked to them by DNA evidence," according to a court filing by the District Attorney's office.

Vilchez Lazo was arrested Thursday after police launched an operation to monitor rideshare vehicles in San Francisco last weekend. He had appeared in court Tuesday to face charges.

He has no criminal history and is being held without bail.

Detectives were looking for suspicious drivers when they pulled Vilchez Lazo over and obtained a DNA sample. They matched his DNA to evidence from a sexual assault reported in June, police said in a statement.

"This was a very proactive investigation. We had a joint task force in place along with SFPD to apprehend the suspect," said Alex Bastian, deputy chief of staff at the San Francisco District Attorney's Office.