A Texas man is charged with aggravated sexual assault he allegedly committed in Yellowstone National Park last fall, according to court documents.

Micah Nathanial Heck of Claude, Texas, pleaded not guilty to the single count against him during his initial appearance before U.S. Magistrate Judge Kelly Rankin in Cheyenne on Thursday.

The indictment, handed up by the federal grand jury in November, says Heck forced a female to engage in a sexual act in September.

However, the indictment does not give any further details about where the assault occurred in the park, the circumstances, or the investigation.

Wyoming U.S. Attorney's Office spokesman Mark Trimble said other information remains confidential per rules about federal grand juries.

Heck was arrested in Claude on Dec. 12 and sent to Wyoming.

Minutes of the initial appearance and arraignment say Heck remains in custody and will have a formal custody hearing on Jan. 23. His trial is set for March 12 before Chief U.S. District Court Judge Nancy Freudenthal.