Lax oversight by the U.S. Agriculture Department and confused food safety inspectors were to blame for imports of 42,000 pounds of Canadian beef products in 2004 that violated a U.S. mad cow disease ban, federal investigators said on Wednesday.

The USDA’s Office of Inspector General issued a report on the 2004 import mistakes less than a month before the federal government is scheduled to further lift restrictions on beef and cattle trade with Canada.

The report analyzed how the USDA mistakenly allowed processed Canadian beef products into the United States between August 2003 and April 2004. Some federal meat inspectors were confused by Washington’s announcement in August 2003 to partially reopen the U.S. border to boneless beef from young Canadian cattle, the investigators found.

The United States banned all Canadian cattle and beef products after Canada discovered its first native case of mad cow disease in May 2003. In August 2003, the USDA decided to allow shipments of boneless beef from young Canadian cattle, which are thought to carry little risk of the disease.

But some U.S. meat inspectors independently began allowing shipments of other Canadian beef products such as cattle tongues, hearts, kidneys and lips, the report said.

“Agency officials asserted that they believed that they could add products to the list of the risk factors and risk levels associated with such products were consistent with the products listed in the initial announcement,” the 50-page report said.

The USDA inspector general said it identified 42,000 pounds of product with “questionable eligibility” that entered the U.S. market.

That volume is much less than the 3.5 million pounds initially estimated by R-CALF United Stockgrowers of America, which first discovered USDA’s mistake. The activist group won a court order in April 2004 to halt the Bush administration from easing its Canadian ban further.

The USDA has said the banned products that did enter the U.S. market from August 2003 through April 2004 did not pose a health risk to consumers.

The USDA said it agreed with many of the recommendations of the inspector general, including closer monitoring of import permits and the immediate posting of import policy changes on the Internet.

The USDA is scheduled on March 7 to begin allowing imports of more Canadian beef products as well as shipments of Canadian live cattle under 30 months of age.