Fingerprinting errors made by U.S. Census Bureau employees may have resulted in the hiring of 200 people with criminal backgrounds to conduct door-to-door canvassing, according to the Government Accountability Office.

In testimony before a Senate subcommittee on Wednesday, GAO Director of Strategic Issues Robert Goldenkoff said tens of thousands of temporary census workers were improperly fingerprinted by bureau employees -- including individuals with extensive criminal records.

"It is possible that more than 200 people with unclassifiable prints had disqualifying criminal records but still worked, and had contact with the public during address canvassing," he said.

Goldenkoff's testimony, part of a larger progress report on the bureau's implementation of the 2010 Census, identified key pitfalls in the hiring of the nearly 1.4 million temporary workers needed to go door-to-door to count every person in the U.S. -- including "weaknesses in the bureau's information technology."

The bureau implemented fingerprinting for the first time in 2010 to better screen its workers. According to the new guidelines, bureau employees are directed to obtain two sets of fingerprint cards for each prospective worker -- and then send them to the bureau's processing center in Jeffersonville, Ind., where are they scanned and submitted to the FBI. If the candidate is found to have a criminal record, making him ineligible for employment, the bureau is "to either terminate the person immediately or place the individual in nonworking status until the matter is resolved."

If the first set of prints is deemed "unclassifiable," the bureau's processing center must send the second set of fingerprints to the FBI for processing.

Goldenkoff testified that of the 1,800 workers with criminal backgrounds, 750 -- or 42 percent -- were terminated because of their records, which included crimes like rape, manslaughter and child abuse.

But about 22 percent of the 162,000 hired so far to conduct the census had "unclassifiable prints" that could not be processed by the FBI because of errors that occurred when the prints were made. Goldenkoff said that, as a result, it was possible 200 individuals with such unclassifiable prints had criminal records but worked anyway.

"Applying these same percentages to the approximately 600,000 people the bureau plans to fingerprint for non-response follow-up, unless the problems with fingerprinting are addressed, we estimate that approximately 785 employees with unclassifiable prints could have disqualifying criminal records but still end up working for the bureau," he said.

The GAO said the Census Bureau is working to address the errors by improving the image quality for the fingerprints and by improving instruction manuals for its workers.