The killing of Cecil the lion in Zimbabwe by American dentist and trophy hunter Walter Palmer is being investigated by the U.S. Fish and Wildlife Service to see if it was part of a conspiracy to violate U.S. laws against illegal wildlife trading, a source close to the case said.
The service is probing the killing under the Lacey Act, which bars trading in wildlife that has been illegally killed, transported or sold, the source said on Thursday.
Palmer, whose practice is in suburban Minneapolis, has admitted to killing the 13-year-old lion and tourist attraction, in July. Questions have been raised by the Zimbabwe government and animal conservationists about Cecil's death outside the Hwange National Park, where he was the head of two lion prides.
The best known lion in Zimbabwe is said to have been lured from the park with bait, shot with an arrow, tracked for 40 hours, shot dead with a rifle and then beheaded and skinned.
Cecil was wearing a GPS collar as part of a research project run by Oxford University.