WASHINGTON — The U.S. Fish and Wildlife Service wants to talk to Walter Palmer. But it can’t find him.

Investigators for the service have knocked on the front door of Palmer’s house, stopped by his dental office, called his telephone numbers and filled his inbox with emails. Palmer, a hunting enthusiast who illegally killed a rare African lion in Zimbabwe early this month, couldn’t be lured out of hiding.

“I’m sure he knows” the government is looking for him, said Ed Grace, chief of law enforcement for the U.S. Fish and Wildlife Service. “We’ve made repeated attempts to try and get in contact with him.”

Palmer, a dentist in Minnesota, has fallen off the radar since Tuesday, when reports first surfaced identifying him as the hunter of Cecil the lion, a celebrity in Zimbabwe. In one of his only public statements, Palmer said Tuesday “I deeply regret” killing “a known, local favorite” and that he relied on local guides. He said he was led to believe the hunt was legal.

“I have not been contacted by authorities in Zimbabwe or in the U.S. about this situation, but will assist them in any inquiries they may have,” Palmer said at the time.

Palmer has had plenty of time since to contact U.S. authorities, Grace said. He should know how to reach the agency “because we convicted him for lying about a bear kill” in Wisconsin in 2009, Grace said. Federal officials want to get Palmer’s version of what went wrong in a hunt that killed a rare lion with a black mane. Cecil was iconic in Zimbabwe.