Yes. If an ongoing investigation reveals that additional charges are warranted, the police, the district attorney’s office, or a grand jury can choose to charge you with additional offenses even if you have already been charged.  It is important to avoid all actions that might incriminate you of further crimes. These include talking to the police (you have the right to tell them you cannot talk without your lawyer), talking to other people about the case, and posting about your case on social media. Keep quiet in public, and work with an experienced criminal defense lawyer who can do all the talking for you.