The Peanut Corporation of America discovered that their peanut products tested positive for salmonella 12 times in 2007 and 2008.
They are accused of "lab shopping" If the product tested positive at one lab, they would take it to another. If the other lab reported it clean, they would use the product. It is general practice that if this happens, to assume it is tainted.
There have been 502 reports in 43 states of this strain of salmonella. There have been 8 reported deaths. Peanut Corp defended their process and labs, along with denying any lab shopping.