Struggling supermarket Morrisons suffered a fresh blow today after payroll data relating to thousands of employees, including bank account details, was stolen and published on a website.
It comes a day after Britain's fourth biggest supermarket tumbled to a £176 million annual loss and issued a profits warning, sending shares down by 12%.
Morrisons said police had been informed of the data theft, which affects staff from all levels of the organisation including the board, but would not comment on whether chief executive Dalton Philips was among them.
The supermarket said it became aware of the data theft last night, hours after it announced financial results to the City and that Mr Philips was leading the response.
It wrote to all employees with an email address to inform them of the data theft, while managers were also informing workers at its sites.
The company posted a Facebook statement, but some staff voiced disquiet that they learned of the breach in this way.
It said: "We are very sorry that this has happened. We will ensure that no colleague will be left financially disadvantaged as a result of this theft."
Morrisons did not say how many of its 130,000 employees were affected.
The supermarket said in a statement: "On Thursday March 13 Morrisons was made aware that data from its staff payroll system had been stolen, published on the internet and sent on a disc to a newspaper.
"This data theft included bank account details. Morrisons immediately ensured it was taken off the website.
"Initial investigations suggest that this theft was not the result of an external penetration of our systems. We can confirm there has been no loss of customer data and no colleague will be left financially disadvantaged.
"We have already informed our colleagues about the theft and we are helping them take the appropriate actions to safeguard their personal data."
Morrisons said it was urgently reviewing internal data security measures.
It was working with cybercrime authorities and police to identify the source of the theft and experts had been brought in to ensure staff did not suffer financial losses.
The supermarket has also informed UK banks of the data theft and is working them to help them maintain account security, and it is setting up a helpline for employees.
A Facebook post for staff said: "The information included names, addresses and bank account details of colleagues. This affects colleagues from all levels of the organisation.
"We are taking this extremely seriously. Dalton Philips is leading the response."
But one person commented on the site: "I haven't been informed of this and shouldn't have to read it on here."
The criminal inquiry into the data theft from Bradford-based Morrisons is being led by West Yorkshire Police.
Detective Chief Inspector Nick Wallen said: "We are aware of the situation and are supporting Morrisons and their investigation into these matters."
It is the latest blow to Morrisons, a day after it announced that it had plunged into the red for the year to February 2, a year after reporting pre-tax profits of £879 million.
Earnings were wiped out amid declining sales and exceptional costs of £903 million from write-downs on the value of its stores and the planned sale of its poorly-performing children's wear retailer Kiddicare.
Like-for-like sales fell 2.8% as Mr Philips pledged a fresh strategy to take on the threat from discounters Aldi and Lidl by slashing prices.
He said the grocery sector was facing the biggest structural shift since the advent of supermarkets in the 1950s.
Mr Philips said Morrisons had the most to lose as shoppers were now choosing to save by using the likes of Aldi and Lidl even if they were no longer struggling to make ends meet as the economy improved.
The store is to invest £1 billion over the next three years to improve value and competitiveness and will also launch a new loyalty card scheme.
It began rolling out an online grocery offering just eight weeks ago, many years later than rivals, and is also concentrating on increasing its smaller convenience stores while scaling back new supermarket plans - expecting not to build any after 2015/16.