Last month’s fire aboard the Navy’s USS Bonhomme Richard is being investigated as a potential case of arson.

A senior Navy official told the New York Times that a joint investigation between the Naval Criminal Investigative Service and the Bureau of Alcohol, Tobacco, Firearms, and Explosives has questioned a sailor who is considered to be a suspect. The sailor, who has not been publicly identified, has not been charged, and no motive has been established. The investigation is reportedly expected to be completed by the end of next month.