Tesco, Sainsbury's, Aldi and Marks & Spencer (M&S) has said they had launched investigations into what one retailer called "unacceptable" allegations of food safety and hygiene offence.
M&S and Aldi have suspended trade with the 2 Sisters site in West Bromwich after an undercover report from the Guardian and ITV alleged staff altered slaughter dates, and repackaged and resent chicken returned to the meat processor.
"We have commenced an immediate investigation into these allegations and will not be taking any more product from this site until it has concluded to our satisfaction," said a spokesperson from M&S.
"The standards shown in the footage are unacceptable; we take hygiene and traceability very seriously and have extremely high production standards."
The M&S spokesperson said the retailer would continue to sell chicken purchased from other 2 Sisters sites.
The Guardian and ITV sent undercover workers to 2 Sisters' factory in West Bromwich, and alleged the following: chicken returned by supermarkets had been repackaged and resold; meat was dropped on the factory floor and returned to the production line; slaughter dates were changed and use-by labels tended to reflect the freshest, not oldest, batch of chicken, which could have led to consumers buying meat past its sell-by date.
'Extremely serious' allegations, says Tesco
These allegations have sparked supermarkets to launching probes into the allegations facing 2 Sisters.
"We operate to the highest possible food quality and safety standards, carrying out our own regular audits at all of our suppliers to ensure these standards are maintained," said a Tesco spokesperson.
"As such, we take these allegations extremely seriously and will be carrying out our own rigorous investigation."
An Aldi spokesperson said:"We have suspended supply from this site while we carry out an urgent investigation into these allegations. We expect all suppliers to adhere to the highest possible food hygiene and traceability standards at all times."
A Sainsbury's representative added: "All of our suppliers are expected to meet our high standards. We are concerned by these allegations and are investigating."
It is unclear whether Tesco or Sainsbury's will follow M&S by suspending trade with the 2 Sisters West Bromwich plant, pending the investigation outcome.
It is also unclear how long the investigations will take.
As the allegations hit the headlines on Thursday 28 September, the Food Standards Agency (FSA) sent inspectors to the plant who found no evidence of breaches.
Heather Hancock, chairman of the FSA said: "We take any allegations of inaccurate labelling and breaches in hygiene regulations very seriously. Should we find any evidence of any risk to public health, any products on the market which we believe to be a cause of concern will be urgently removed from sale."
Lidl, the fifth supermarket believed to be supplied by the Midlands-based factory, has been approached for comment.
Butchery chain Crawshaws which entered into a supply chain agreement with 2 Sisters earlier this year is also investigating the allegations.
A spokesperson said: "Crawshaws operates to the highest standards of food safety and we expect all our suppliers to do the same. We are looking into this matter as a priority."
2 Sisters: hygiene 'number one priority'
In response to the allegations, a 2 Sisters spokesperson said: "We have been made aware of several broad allegations made by The Guardian/ITV in relation to inappropriate procedures, food safety and hygiene issues at two of our poultry processing facilities. We view these allegations extremely seriously.
"However, we have not been given the time or the detailed evidence to conduct any thorough investigations to establish the facts, which makes a fulsome response very difficult. What we can confirm is that hygiene and food safety will always be the number one priority within the business, and they remain at its very core.
"We also successfully operate in one of the most tightly-controlled and highly regulated food sectors in the world. We are subject to multiple and frequent unannounced audits from the FSA, BRC, Red Tractor, independent auditors as well as our customers. By example, our facility in the West Midlands under investigation received nine audits (five unannounced) in the months of July and August alone.
"However, we are never complacent and remain committed to continually improving our processes and procedures. If, on presentation of further evidence, it comes to light any verifiable transgressions have been made at any of our sites, we will leave no stone unturned in investigating and remedying the situation immediately."