British Airways has revealed that another 185,000 customers may have had personal details stolen in a data breach.

Customers who made reward bookings using a payment card between 21 April and 28 July this year may be at risk, British Airways owner International Airlines Group (IAG) said in a statement to the stock market.

British Airways revealed last month that it had identified 380,000 payment cards at risk, although on Thursday it downgraded its estimate to 244,000 affected.

On top of that, hackers may have stolen names, addresses, email addresses, card numbers, expiry dates, and card verification value (CVV) numbers for another 77,000 customers, British Airways said, potentially allowing purchases to be made.

Another 108,000 may have had details stolen not including the CVV, the three-digit code which acts as an extra layer of protection for online transactions.

All affected customers will be contacted via email before 5pm on Friday, a spokesperson for British Airways said.

The spokesperson said the airline was unable to confirm details of how the data breach occurred, in order to avoid compromising the police investigation.

IAG said it does not have “conclusive evidence” that any data has been removed from its systems, but advised customers to contact their bank or card provider “as a precaution”.

British Airways has been “working continuously with specialist cyber forensic investigators and the National Crime Agency to investigate fully the data theft”, IAG added.

However, British Airways said it has not yet received any verified reports of fraud in relation to the data breach.

Alex Cruz, chairman and chief executive of British Airways, previously pledged to compensate any customers who suffer “financial hardship” because of the breach.

He said the firm was “deeply sorry”, saying he takes “the protection of our customers’ data very seriously” when the possible theft was first announced in September.

The breach marked the latest in a series of major computer issues for British Airways, after a systems outage in May 2017 forced it to cancel all flights for a day from London’s Heathrow and Gatwick airports.