US safety officials are investigating salmonella contamination in pistachio products sold by Setton Pistachio of Terra Bella, the second-largest pistachio processor in the US.

The company stopped all distribution of processed pistachios this week and is to issue a voluntary recall involving around one million pounds of its products.

The recall affects certain bulk roasted inshell and roasted shelled pistachios shipped on or after 1 September 2008.

The FDA and the California Department of Public Health (CDPH) are investigating the contamination, which involves multiple strains of salmonella.

As the pistachios were used as ingredients in a variety of foods, it is likely the recall will impact a number of products.

The FDA said that the investigation at the company is “ongoing” and may lead to additional pistachio product recalls.

To date several illnesses have been reported by consumers that may be associated with the pistachios. The FDA said it is not yet known whether any of the salmonella strains found in the pistachio products are linked to an outbreak but that it is conducting genetic testing of the samples to “pursue all links”.

The FDA is recommending that consumers avoid eating pistachio products until further information is available about the scope of affected products.

The FDA first learned of the problem on 24 March when it was informed by Kraft Foods that its Back To Nature Trail Mix was found to be contaminated with salmonella.

Kraft had identified the source of the contamination to be pistachios from Setton and conducted a recall.

Setton said it is “committed to quality products and consumer safety”, and is taking “aggressive action” to prevent the need for any future recalls of its products.