Jason Stubbs, 27, was arrested on Wednesday at a local school where he was teaching, after officials learned of an alleged incident on Monday.
Stubbs was arrested on felony charges of having sexual contact with a minor under the age of 14. The charges also include sodomy and sexual penetration by force.
The alleged incident took place this summer. Investigators say Stubbs used social media to communicate and meet minors, and that's why officials fear there may be more victims.
"If you look at his friends, and he has minors, or what they appear to be minors, that those people can be victims," said Deputy Albert Martinez with the Riverside County Sheriff's Department.
Stubbs previously worked for the Jurupa Valley School District before he started working for the Fontana School District last year. Investigators say he had no prior run-ins with the law.
Stubbs was released after posting bail. He is due back in court Oct. 16.
For parents, the allegations of sexual misconduct by a substitute teacher were cause for concern.
"I think they should do more background checks and different types of checks because it's happening too often. Too many different districts, too many different counties," said Lawanda Woods, a parent.
If you have any information about additional victims, you're urged to contact the Riverside County Sheriff's Department at (951) 955-2600.