Criminal charges may be filed against a stepsibling of 18-year-old Anna Kepner, a Florida high school cheerleader found dead aboard a Carnival cruise ship earlier this month, a new court filing suggests.

The disclosure appears in an emergency motion submitted in a divorce case involving Kepner's stepmother, Shauntel Hudson. In the motion — which seeks to reschedule a hearing in the proceedings — Hudson's attorneys write that she has been told by FBI investigators that “a criminal case may be initiated” against one of her minor children.

“An extremely sensitive and severe circumstance has arisen wherein the Respondent/Mother will not be able to testify at the hearing at this time,” the filing states.

CBS News has reached out to Hudson and her attorneys.

Kepner was on a family vacation in the Caribbean with her father, stepmother and three stepsiblings when she was discovered dead on the Carnival Horizon as it was headed back to Miami, where it docked on Nov. 8. Her body was found by a housekeeper under the bed in her stateroom, law enforcement sources told CBS News.

According to family members, Kepner had told them the night before that she wasn't feeling well and returned to her room. When she didn't show up for breakfast the next morning, a frantic search began.

Investigators are now reviewing surveillance video from the ship and analyzing electronic swipe card data that may show who entered the teen's cabin, the law enforcement sources said. They are also examining Kepner's cellphone records. The FBI and ship security are also conducting interviews with other passengers, crewmembers and Kepner's family.

In a statement, Carnival Cruise Line said it is cooperating with the federal investigation. The FBI has jurisdiction because Kepner is a U.S. citizen and the death occurred in international waters. The Miami FBI office is working closely with Carnival security.

Carnival also said the FBI has told it there is no related threat to safety aboard the ship on its current voyage.