The family of Otto Warmbier declined to have an autopsy performed, leaving the late University of Virginia student's cause of death undetermined.
The Hamilton County (Ohio) Coroner's Office confirmed to CNN that the Warmbier family's "objection to an autopsy was honored," and only an external examination was performed.
The family's objection to an autopsy has left many wondering what caused Warmbier to die a few days after he returned to the U.S. from North Korea.
Warmbier was sentenced to 15 years of hard labor last March, for allegedly stealing a propaganda poster from a hotel in North Korea.
North Korean officials said he contracted botulism and fell into a coma shortly after taking a sleeping pill.
When Warmbier returned to the U.S., doctors estimated that he had been in a coma for nearly a year.
They described Warmbier's condition as a state of "unresponsive wakefulness" and said he suffered a "severe neurological injury" of unknown causes.
Warmbier's father, Fred Warmbier, accused North Korea of abusing his son and said its "awful torturous mistreatment" led to his death.
Warmbier's death prompted lawmakers, including Sen. Marco Rubio (R-FL) to condemn North Korea for its treatment of the American student.