Updated: 5:50 p.m. PT April 20, 2007

WASHINGTON - Imported ingredients used in recalled pet food may have been intentionally spiked with an industrial chemical to boost their apparent protein content, federal health officials suspect.

That’s one theory being pursued by the Food and Drug Administration as it investigates how the chemical, melamine, contaminated at least two ingredients used to make more than 100 brands of dog and cat foods.

http://www.msnbc.msn.com/id/18210224/