Manchester United are being assisted by the UK’s cyber security agency after a cyber attack left the club unable to fully restore its systems.
The club said it had been hacked last week, adding they were not “aware of any breach of personal data associated with our fans and customers”.
It reported the attack to the Information Commissioner’s Office, as required by law.
Staff at the Premier League club still do not have access to email, and the National Cyber Security Centre (NCSC) is now involved.
A spokesperson for the agency said: “The NCSC is aware of an incident affecting Manchester United Football Club and we are working with the organisation and partners to understand impact.”
Manchester United have since repeated that it does not believe any fan data was impacted.
They would not say who was “responsible for the attack or the motives”.
“This attack was by nature disruptive, but we are not currently aware of any fan data being compromised,” the club added.
“Critical systems required for matches to take place at Old Trafford remained secure and games have gone ahead as normal.”
The club could face a fine from the Information Commissioner’s Office if any fan data has been compromised.
On 13 November, Ticketmaster was handed a £1.25m fine after it was found to have failed to keep customers’ data secure in a 2018 attack.
The NCSC said earlier this month that it had defended the UK from more than 700 cyber attacks in the last year, adding it dealt with three times as many ransomware attacks compared to the year before.
It also said that criminals were adapting their approach during the attacks, threatening targets that they might leak data publicly, unless a ransom is paid.