The Ministry of Justice is suspending one of the suppliers of meat to prisons after it discovered that Halal pies and pasties sourced from a properly Halal certificated supplier may contain traces of non-Halal meat, it said.
The products concerned have been withdrawn immediately, a spokesman said.
He added: "All prisons have been informed about this very regrettable incident and we reported this issue to the Food Standards Agency immediately.
"We are taking immediate steps to suspend the contract with the relevant subcontractor."
Justice minister Jeremy Wright said: "This is an absolutely unacceptable situation and one which we regret greatly. Clearly this must be distressing for those affected and they can be reassured we are doing everything we can to resolve the situation. The Prison Service is investigating this as a matter of urgency."