The company said it was now pulling a total of nine brands of its dry dog food from the shelves. In April, it began the recall by pulling three brands.

The salmonella cases were found in humans who may have had contact with dogs or dog foods prior to their illness.

The Centers for Disease Control (CDC) and Prevention is still investigating the outbreak, but said cases could be due to a number of causes, including people touching the dog food and then handling their own food; cross-contamination through the use of dishes or utensils that came in contact with the dog food, but were not properly cleaned; or from direct contact with a dog carrying the disease.

The additional brands have been recalled as a precaution and none had tested positive for salmonella, according to a statement issued by the company on Saturday.

The products were distributed in 16 states, mostly along the U.S. East Coast and Canada.

Several other food companies, including WellPet LLC and Dick Van Patten's Natural Balance Pet Foods Inc, have also recalled brands as a precaution.

Diamond first started pulling some brands of dog food produced at a South Carolina plant after salmonella infections were reported from October 8, 2011, to April 22, and five people were hospitalized.

Cases were reported in Alabama, Connecticut, Michigan, Missouri, North Carolina, New Jersey, Ohio, Pennsylvania and Virginia.

Seven of 10 sick people said they had contact with a dog in the week before becoming sick.

And five of sickened people recalled the type of dog food with which they had contact, the Centers for Disease Control (CDC)and Prevention previously said in a statement.

(Reporting by Paul Thomasch; editing by Todd Eastham and Andre Grenon)

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