Taking the heat for alleged misconduct by her predecessor, Interior Secretary Gale Norton admitted Wednesday that Indian trust fund records may never be fully accounted for because many of the records have been destroyed.

"In general terms, trying to piece together all the information since 1887 is going to be a very difficult job," Norton testified in District Court Wednesday. "It will be blocked in some cases because a particular piece of information has been destroyed."

In some cases, documents were not stored properly and they "crumbled with age," Norton said.

Norton's agency has been ordered to track debts owed to Indian tribes from a $500 million-a-year trust fund set up to distribute royalties earned from Indian-owned land taken by the government. Thousands of Native Americans have filed a class-action suit to trace the fund's earnings. Norton is facing a contempt of court charge for allegedly concealing the failures of the Indian trust funds' accounting systems.

She said her agency has tried to follow a judge's order to fix management problems with the trust fund system. Progress has been made, though more needs to be done, she said.

"We have tried to use appropriate standards and aspire to a high level of accounting responsibility," Norton said. "I'm not sure if in every instance we have met that standard."

U.S. District Judge Royce Lamberth advised Norton's attorney to "throw yourself on the mercy of the court" for Norton's "clearly contemptuous" approach to the case, one that began during the term of Clinton Interior Secretary Bruce Babbitt.

In 1999, Lamberth held Babbitt and then-Treasury Secretary Robert Rubin in contempt and fined them $600,000 for failing to turn over documents in the 5-year-old class-action lawsuit brought by Indian landowners. Those fines, as well as any Norton may be issued, will be paid by the department.

The trust accounts represent some 45 million acres that were held by the federal government in trust for individual Indians following an 1887 federal law that divided up reservation land.  The government may not tax or sell the land and must approve any leases for mining, grazing and timber contracts.

Indian groups charge that money earned from the land and intended for Indian beneficiaries was lost, misappropriated, stolen or never collected. The Indians' attorneys claim the government owes 300,000 Indian account holders more than $10 billion.

The government acknowledges mismanagement of the accounts, and Norton has proposed creating a new bureau in the Interior Department to manage the money. Indian leaders prefer to strip authority from the Interior Department and assign account management to a receiver outside the department.

The top congressionally appointed trust official, Thomas Slonaker, has testified that he did not have faith in the Interior Department's reform efforts.

Norton and Assistant Secretary of Indian Affairs Neal A. McCaleb, also facing contempt charges, are in the concluding stages of the contempt trial started in December and offered by Lamberth as an attempt to show good faith to prevent possible further charges by the Indian groups.

The Associated Press contributed to this report.