A food safety investigation into a 2 Sisters poultry processing plant in West Bromwich has been extended to other plants operated by the company.
The Food Standards Agency (FSA) launched its initial investigation after undercover footage was broadcast of workers at the West Bromwich plant changing kill dates on crates of poultry.
Footage also showed workers mixing batches of old and new stock.
The FSA said it has decided to extend its investigations to other 2 Sisters poultry plants in England and Wales on Friday (6 October).
FSA chairman Heather Hancock said: “Consumers deserve food they can trust, and can be reassured that we take allegations of poor practice very seriously.
“Although our initial inspection found no risk to public health, we are broadening our investigations until we are satisfied that this is truly the case.”
The undercover footage was obtained by ITN and The Guardian.
The FSA said its initial inspection had not identified food safety issues at the West Bromwich processing plant.
But it added that the inspection highlighted issues requiring management attention – for example, in relation to some aspects of staff training and stock control.
The FSA said it is working with the major retailers supplied by 2 Sisters, as well as reviewing information from various other sources.
It has also written formally to ITN and The Guardian to request the full evidence taken by their undercover investigation, including the footage taken and witness interview transcripts.
Ms Hancock said: “I’m disappointed that ITN and The Guardian have not yet provided the information that they committed to share.
“I would urge anyone who has evidence to share to bring it directly to us.”