An animal autopsy will be conducted by federal officials to help determine what happened to a young green sea turtle that was found dead in a charcoal bin at Maili Beach Park.

Green sea turtles are considered threatened under the U.S. Endangered Species Act. Penalties for killing a threatened species range from $3,500 to $13,000, depending on circumstances. Sea turtles also come under the protection of Hawaii statutes and rules.

The juvenile, with a shell measuring 21 inches across, was found Sunday in the charcoal bin among some rubbish, and was retrieved by marine turtle stranding network volunteers.

The necropsy has yet to be scheduled, said Patrick Opay, endangered-species branch chief with the National Oceanic and Atmospheric Administration Fisheries Pacific Islands Regional Office.

Officials are hoping the necropsy will show what killed the animal. Opay said the top reasons for turtle deaths are fishing gear and fibropapillomatosis, the tumor growth disease. There didn’t appear to be any evidence of either, Opay said, but the necropsy will make that determination.

Despite an overall declining trend globally, green turtle population growth rates vary regionally. The Hawaiian green turtle population is increasing, having risen 53 percent over the past 25 years.

In 2012 the Association of Hawaiian Civic Clubs petitioned the government to study whether Hawaii’s green sea turtles might have recovered to the point where they no longer need Endangered Species Act protections.

The clubs said delisting the turtles would return management of the animals to the state and allow more people to take active roles in taking care of them.

But federal officials last week said the green turtles should continue to be classified as threatened because their population is small and nearly all of them nest at the same low-lying atoll.

Hawaii has fewer than 4,000 nesting green sea turtles, and 96 percent of them nest at French Frigate Shoals in the Northwestern Hawaiian Islands, making them vulnerable to outbreaks of disease, rising sea levels and other threats, officials said.

Green sea turtles nest on beaches and feed in the coastal areas of the main Hawaiian Islands, eating mostly sea grass and algae. Adult females return to the same beaches where they were born every two to four years to lay eggs, sometimes migrating hundreds or thousands of miles.

Anyone who encounters a stranded or entangled sea turtle, dead or alive, is asked to call NOAA’s marine turtle stranding network at 725-5730.