A senior Interior Department official was awarded his own buffalo to hunt on a billionaire's ranch a month before his office designated Houston as a port for exotic wildlife, a move that benefited the ranch owner.

The involvement of the official, David P. Smith, "was inappropriate and violated the appearance standard," the department's inspector general said in a report. Smith resigned last week to begin a new law firm.

Smith was deputy assistant secretary for fish, wildlife and parks when he shot and killed the buffalo at a 5,000-acre ranch owned by Texas billionaire Dan Duncan. The hunt took place during the first weekend of December 2004.

"Dan doesn't have any business before the Interior," Smith told The Associated Press on Wednesday. "Every time I've ever been on Dan's ranch, Dan has never asked me to do anything for him or for anyone else."

Smith said the aging buffalo he shot had torn up some ranch equipment, rammed vehicles and terrified ranch hands. He said he drove in a pickup to within 100 yards of the buffalo — the official symbol of the Interior Department — and shot it between the eyes with a .30-caliber bolt-action rifle.

Smith left the department last Friday. A department spokesman declined to comment on Wednesday, saying it was a personnel matter.

No disciplinary action was taken against Smith, who said he had submitted his resignation letter in mid-June.

"The allegation that somehow the designation of the port was awarded in exchange for hunting the buffalo is preposterous," he said. "It benefits anyone who brings anything through the port of Houston. It doesn't benefit him (Duncan) more than anyone else."

After the department's internal watchdog began investigating, Smith reimbursed the ranch $3,170.54 for the buffalo's shoulder mount, skull and tanned hide and for 20 pounds of meat. He also had the animal's hooves made into bookends.

The department on Jan. 5, 2005, designated Houston, Memphis, Tenn., and Louisville, Ky., as official ports for bringing exotic wildlife animals and trophies into the United States. That brought to 18 the number of such ports, which can save big-time hunters and other noncommercial importers time and about $200 in fees for each shipment.

Smith, a lawyer from Austin, Texas, was a regular visitor to Duncan's Double "D" Ranch near Smithville, Texas.

Duncan, an energy entrepreneur, has hunted around the globe, seeking ever more exotic animal species. He has traveled dozens of times to Africa, Europe and Asia and is a major contributor to Safari Club International, a group that seeks to protect the freedom to hunt and ensures that plentiful wildlife exists for hunters.

Smith joined the Interior Department in January 2001 when President Bush took office. An agency news release issued upon his promotion 18 months later described him as an avid hunter, fisherman and outdoorsman.

The undated agency report, obtained through a Freedom of Information Act request by U.S. News & World Report, said the Justice Department had declined to prosecute.

"This investigation found that appropriate administrative procedures were followed in the designation of the port of Houston; however, Smith's involvement, given his personal relationships with individuals who benefited directly from the port's designation, was inappropriate and violated the appearance standard," the report said.

Most of the 400,000 buffalo in the United States are raised as livestock.