LOS ANGELES (AP) — A Mexican Uber driver living in the U.S. illegally was charged Monday with raping, assaulting and robbing young women in California, prosecutors said.

Alfonso Alarcon-Nunez’s four alleged victims are between 19 and 22 years old and three were intoxicated when they were assaulted, San Luis Obispo County District Attorney Dan Dow told reporters.

Officials said Alarcon-Nunez was not always driving for Uber when he picked up those women but said the alleged crimes show that the company should improve its driver screening process, Dow said.

Alarcon-Nunez, 39, faces 10 criminal charges including forcible rape, rape of an intoxicated victim, oral copulation of an intoxicated victim and first degree burglary. It wasn’t immediately known if Alarcon-Nunez has an attorney. His arraignment was scheduled for later Monday.

Detectives are looking for potential witnesses and trying to determine if there are additional victims in San Luis Obispo and Santa Barbara counties northwest of Los Angeles, where the Alarcon-Nunez had been driving for Uber since September of last year, Dow said. He had a valid California license issued in 2015.

Prosecutors said Alarcon-Nunez solicited rides as an Uber driver, targeting drunk women. Then he drove women to their homes, assaulted them, and stole property including cellphones, computers, and jewelry, officials said.

He collected his fare payments through the smartphone app Venmo to disguise his identity and his Uber records, officials said.

Alarcon-Nunez has also gone by the name “Bruno Diaz” and his Venmo username was “Brush Bat,” prosecutors said.

Predators in cars parked outside bars or restaurants “jump in front of the actual Uber driver and they will take someone unsuspecting to their home. And that’s a way of putting someone at risk, and in this case that’s exactly what’s alleged to have happened,” Dow said.

Dow urged Uber users to make sure they are getting in the car of the correct driver by verifying the license plate and other information provided to clients.

DNA evidence helped lead detectives to Alarcon-Nunez, who was arrested at his Santa Maria home last week, Dow said. The alleged crimes are said to have occurred in December and January in San Luis Obispo, a city of about 45,000 with a large population of college students.

Dow urged Uber and other ride-hailing companies to beef up background checks. Uber spokesman Michael Amodeo did not immediately respond to an email seeking comment.

Alarcon-Nunez returned to the U.S. illegally after a voluntary deportation from New Mexico in 2005, officials said. Dow did not have details about why he was deported or whether he has a criminal record in the U.S.

Alarcon-Nunez’s immigration status will not have a bearing on the prosecution, Dow said. He could face life in prison if convicted on all charges.

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