Large companies are improperly getting billions of dollars in government contracts meant for small business, a preliminary investigation by the U.S. General Accounting Office has found.

Although the GAO probe is not complete, agency officials have advised staffers with the House Committee on Small Business that the amount of improperly awarded contracts is in the "billions of dollars," Wendy Belzer, a spokeswoman for Rep. Nydia Velazquez of New York, the ranking Democratic committee member, said Tuesday.

The GAO is the investigative arm of Congress. The agency launched the probe last year amid complaints by a Novato small-business group to Sen. Barbara Boxer, D-Calif., and Rep. Juanita Millender-McDonald, D-Calif.