New charges filed against someone already incarcerated can come from two very different directions, and figuring out which one applies here determines where you look for information.
The first possibility is an internal disciplinary matter handled within the facility by a Disciplinary Hearing Officer. This covers rule violations and incidents that occur inside the house of corrections itself. If that is the case, call the facility and ask to speak with his counselor. Explain that you received a call about new charges and ask what you can find out. They may not share specific disciplinary details, but a politely worded inquiry sometimes produces useful information. His counselor is your best internal contact for anything happening within the facility.
The second possibility is that an outside jurisdiction, meaning a county district attorney, a state attorney, or a federal agency, has filed new criminal charges based on something connected to his case or conduct. If that is what happened, the charges were filed in a specific court and that is where the public record lives. You need to identify which agency brought the charges and in which county or jurisdiction they were filed. Once you know that, the Clerk of the Court in that jurisdiction can tell you what is on the docket.
TruthFinder can be a useful starting point for pulling together public record information quickly if you do not yet know which jurisdiction is involved.
The most direct path to the truth, if all else fails, is a straight conversation with your husband. Whatever is happening, he knows more than anyone else about the source of the new charges.