LOS ANGELES — DeFranco & Sons, a producer of fresh produce and nuts, has issued a voluntary recall for bulk and consumer-packaged in-shell hazelnuts and mixed-nut products containing in-shell hazelnuts.

The products in question have been linked to seven cases of Escherichia coli 0157:H7 in Michigan, Minnesota and Wisconsin. The nuts were distributed throughout the United States and in Canada from Nov. 2, 2010, to Dec. 22, 2010, and were sold in 2-lb and 4-lb packages of mixed nuts, 1-lb packages containing only in-shell hazelnuts or in open bins of nuts in grocery stores. The affected products were under the Sunripe and George Packing brands.

The Food and Drug Administration became aware of the problem in late February and is working with the Centers for Disease Control and Prevention and public health and agricultural agencies in states where illness has been reported to investigate the source of the contamination. The F.D.A. also is working with state authorities to take action to address any contaminated product that might still be on the market.