Federal auditors found that nearly half the food manufacturers they surveyed that are supposed to register with the Food and Drug Administration failed to give the agency accurate contact information, according to a report to be released Friday by the U.S. Department of Health and Human Services inspector general’s office.

Companies that manufacture, process, pack or hold food that is eaten in the United States are required by federal law to provide their address and basic contact information to the FDA, so investigators can follow suspect foods through the supply chain.

After interviewing managers at a sample of 130 such companies, however, government investigators found that 48 percent didn’t give the agency accurate information. More than half were unaware companies had to register, and about a quarter provided no emergency contact information, because current rules don’t require it.