An FBI agent told a Senate investigative panel Wednesday that corruption is pervasive among Indian tribes in the United States, but often federal laws are inadequate to prosecute wrongdoers.

Special Agent Richard James Elroy said agents investigating bribery can often prove that money has changed hands between contractors and tribal leaders, but are unable to demonstrate there was the kind of quid pro quo agreement that a prosecutor can use to show that money was in exchange for a favor.He also said state officials would be treated differently than Indian leaders are if corruption in their governments was suspected. "For some reason tribal governments are not included in the code for treatment like state governments would be," he said.

Elroy acknowledged that the Bureau of Indian Affairs is responsible for oversight in Indian reservation business. But he said tribal leaders have had local BIA directors removed by complaining to Washington.

In Tuesday's hearing, secretly taped conversations were played indicating the chairman of the Navajo nation devised a scheme to cover up thousands of dollars in kickbacks from the sale of a 491,000-acre ranch to his tribe.

The voice of tribal chairman Peter MacDonald Sr. was heard in a recording made by real estate broker Byron T. "Bud" Brown in cooperation with a special investigative unit of the Senate Select Committee on Indian Affairs.

Brown, who testified before the panel under a grant of immunity, said he paid MacDonald $25,000 to pay a bank loan and gave him $50,000 in cash and an expensively equipped BMW automobile as his share of profits from the sale of the 491,000-acre Big Boquillas ranch in western Arizona.

In the tape recording of a conversation Nov. 22, 1988, MacDonald tells Brown to say that the $25,000 and car were for his son, Peter MacDonald Jr.

They discuss point by point what Brown should tell investigators.

"It's Rocky that asked you for this 25,000," the senior MacDonald says in reference to his son, nicknamed Rocky. And later, the older MacDonald is heard saying that his son "wanted the car, since he doesn't have a vehicle."

The senior MacDonald wanted to cover up the payments after the local U.S. attorney began an investigation of the sale, Brown told the committee.