A 28-year-old Fontana police officer has been arrested on suspicion of raping a 16-year-old girl, authorities said.

The Fontana Police Department reached out to the San Bernardino County Sheriff’s Department last week for assistance investigating the encounter, which investigators say occurred in 2016.

Detectives from the sheriff’s Specialized Investigation Division, Crimes Against Children Detail, took over the investigation and quickly identified a suspect.

Nicholas Shawn Stark was arrested Thursday on suspicion of rape of a minor by intoxication, the Sheriff’s Department said.

He was released on bail Friday, records show. It was not immediately clear when he is scheduled to appear in court.

Stark is an officer with the Fontana Police Department, authorities said. However, the encounter allegedly took place before he joined the force, according to sheriff’s officials.

“Based on California law, I cannot immediately fire Nicholas Stark,” Fontana Police Chief William Green said in a statement Monday. “He is on paid leave, and that is disgusting. However, I will endeavor to terminate him in the most expeditious manner possible.”

Green said Fontana police learned of the incident last Tuesday — when “one of our captains became aware of a post on social media from a young woman indicating she had been a victim of sexual assault, and the culprit was an officer” — and that he personally asked the Sheriff’s Department to investigate.

“This is not what the Fontana Police Department is about,” he said.

“This act, despite having occurred prior to becoming a Fontana officer, rightfully calls into question the character of the entire department. I understand that,” Green said. “I commit myself, and the 300 men and women I work with, to do what needs to be done to begin repairing the damage.”

Anyone with additional information is asked to contact the Crimes Against Children Detail at (909) 387-3615. Tips also can be left anonymously at (800) 782-7463.