An undocumented Mexican man driving with Uber was arrested Monday for allegedly sexually assaulting at least four intoxicated college-aged women in San Luis Obispo, California, police said.

Alfonso Alarcon-Nunez, 39, is facing 10 felony charges such as first-degree burglary and oral copulation following his Monday arrest. Alarcon-Nunez pleaded not guilty to all allegations, however. The incidents reportedly occurred over the course of four weeks mid-December 2017 in San Luis Obispo.

"What police have reported is absolutely horrifying, and something no person should ever have to experience," Andrew Hasbun, an Uber spokesperson, said in a statement issued to International Business Times. "We have been working with law enforcement to provide them with information for their investigation, and the driver has been permanently removed from the app."

Alarcon-Nunez, a Santa Maria resident who returned to America illegally in 2005 after being voluntarily deported from New Mexico, accepted ride transactions through Venmo to conceal his identity and Uber records, KSBY reported. He would use the username "Brush Bat" on Venmo as he went by the alias "Bruno Diaz."

DNA evidence allowed law enforcement to track down Alarcon-Nunez, ABC News reported. Investigators with the San Luis Obispo Police Department (SLOPD) claim there are more apparent victims that haven't been identified, however. So far, the identified young women are students at California Polytechnic State University and Cuesta College.

"We know there are additional victims," district attorney Dan Dow said in a Monday press conference, according to KEYT. "We don't have their identities right now, so we're combing our evidence for clues, but we're relying heavily on the public. Anybody who feels like they've been victimized after a ride with Uber."

"Anyone who may have ridden with Mr. Alarcon-Nunez would be urged to contact either the San Luis Obispo Police Dept. or call the Crimestoppers line so we can look into every lead," Dow added.

Alarcon-Nunez's bail was set at $1,470,000. He is expected to return to court Jan. 29.

Uber drivers are required to undergo a strict pre-screening process before being hired, with specific regulations set for interested persons in California.

"Every person who wants to drive with Uber in California is required to undergo a pre-screening process," Uber's website read. "The screening, which looks back seven years, is performed on our behalf by Checkr, a third-party background check provider that is accredited by the National Association of Professional Background Screeners."

"Individuals who pass the driving history screen then undergo a national, state, and local-level criminal history check that screens a series of national, state, and local databases," the website continued.

Databases used to screen potential drivers include the U.S. Department of Justice National Sex Offender Public Website, among others. Uber confirmed to IBT that Alarcon-Nunez has a valid California driver's license and passed his criminal background screening, which was conducted by the company's third-party checker.

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