(CNN) Tyson Foods has significantly expanded a recall of its chicken strips over concerns that some might be contaminated with pieces of metal, federal food safety officials said Friday.

The recall now affects more than 11.8 million pounds of frozen, ready-to-eat chicken strip products that were shipped nationwide, up from more than 69,000 pounds when the recall initially was issued in March , the US Department of Agriculture's Food Safety and Inspection Service said in a statement.

The expansion comes after three of six people who complained about finding pieces of metal in certain Tyson products also said they suffered an injury in their mouth, the agency said.

The products now being recalled were produced from October through March 8, and they have "use by" dates of October 1, 2019, through March 7, 2020.

Each of the recalled products have establishment number "P-7221" on the back of the package.

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