Federal health officials are defending their handling of the nationwide salmonella outbreak, telling Congress they had been hot on the trail of a Georgia processor even before they were certain that peanuts were the culprits in hundreds of illnesses.

Stephen Sundlof, who heads the Food and Drug Administration's food safety center, says the agency began investigating the salmonella outbreak before there was a scientific link to a particular food.

In remarks prepared for delivery Thursday to the Senate Agriculture Committee, Sundlof provides details of the FDA's investigation.

The FDA has been criticized by members of Congress and President Barack Obama. Salmonella-tainted peanut products have been blamed for the illness of more than 550 people and the deaths of at least eight.