The British Library has said the final cost of recovery from a recent cyber attack is “still not confirmed”.

The Financial Times reported the library will use about 40% of its reserves after the attack, which was announced in October as a “major technology outage”.

According to the FT, a source said the library will be forced to spend what could equate to £6 million to £7 million – out of £16.4 million in unallocated reserves – to rebuild most of its digital services.

The library outside St Pancras International station, which has one of the largest book collections in the world, said it has its own financial reserves and has not applied for extra funding.

A spokesperson said: “The final costs of recovering from the recent cyber attack are still not confirmed.

“The British Library and its Government sponsor, the Department for Culture, Media and Sport (DCMS), remain in close and regular contact.

“The library always maintains its own financial reserve to help address unexpected issues and no bids for additional funding have been made at this stage.”

In October the institution announced that the National Cyber Security Centre (NCSC) and cybersecurity specialists would investigate the attack.

The next month it was revealed that the attack had led to a leak of employee data.

The Rhysida ransomware group claimed it had access to passports along with other data files.

In a post to X at the time, the institution said: “We’re continuing to experience a major technology outage as a result of a cyber-attack. This is affecting our website, online systems and services, as well as some onsite services too.

“Following confirmation last week that this was a ransomware attack, we now have evidence that indicates the attackers might have copied some user data, and additional data appears to have been published on the dark web.

“We will continue to work with cybersecurity specialists to examine what this material is and we will be contacting our users to advise them of the practical steps they may need to take.”

The library is collaborating with the Metropolitan Police and says analysing data from the breach is likely to take several months.

The attack is still affecting the library’s online systems and services but its physical sites are open.

A reference-only version of its main catalogue will be back online from January 15.

The DCMS declined to comment.