The latest on the controversy surrounding a Minnesota big-game hunter and his guides in Zimbabwe who killed a protected lion (all times are Central):

12:20 p.m.

The law enforcement arm of the U.S. Fish & Wildlife Service says it's trying to reach the Minnesota dentist who killed a protected lion while on a guided hunt in Zimbabwe.

In a statement Thursday, Fish & Wildlife Law Enforcement Deputy Chief Edward Grace re-iterated that the agency is investigating circumstances surrounding the death of lion, named Cecil.

Grace says multiple efforts to contact the dentist, Walter Palmer, were unsuccessful and "we ask that Dr. Palmer or his representative contact us immediately."

Palmer hasn't returned emails from The Associated Press. His office voicemail isn't accepting messages and other listed phone numbers have busy signals.

A public relations professional released a statement Tuesday from Palmer, who said he was with professional guides and thought the hunt was legal. The firm is no longer helping Palmer.

An attorney who represented Palmer in a prior case also has not returned messages.

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9:50 a.m.

Safari Club International is suspending the membership of the Minnesota hunter accused of illegally killing a protected lion in Zimbabwe and wants a "full and thorough investigation" into the lion's death.

The club, which promotes big-game hunting worldwide, issued a statement late Wednesday saying memberships for Walter Palmer and his guide in Zimbabwe, Theo Bronkhorst, will be on hiatus until investigations are complete.

Bronkhorst is facing criminal charges in Zimbabwe over the July 1 killing of the beloved lion named Cecil, who was drawn away from a wildlife preserve and shot by Palmer with a bow and arrow. Palmer has said he believed the hunt was legal.

The Safari Club says "those who intentionally take wildlife illegally should be prosecuted and punished to the maximum extent allowed by law."