An outbreak of salmonella food poisoning traced to peanut products has sickened 666 people and is continuing despite one of the biggest food recalls in U.S. history, health officials said on Tuesday.

But the outbreak of salmonella is still only linked to nine deaths, the U.S. Centers for Disease Control and Prevention said in a statement.

"To date, 19 clusters of infections in five states have been reported in schools and other institutions, such as long-term care facilities and hospitals. King Nut brand peanut butter was present in all facilities," the CDC said in a statement.

King Nut is produced by Peanut Corporation of America, which has gone into bankruptcy and closed two plants in Georgia and Texas after inspectors traced the salmonella outbreaks to them.

Its peanuts were not used in name brands of peanut butter but were ingredients in a wide range of products from peanut butter crackers to dog treats and bird seed.

"To date, more than 2,100 products in 17 categories have been voluntarily recalled by more than 200 companies, and the list continues to grow," the U.S. Food and Drug Administration said in a statement.

FBI officials in Atlanta and Virginia said earlier this week they had joined the FDA in a criminal investigation of the company.