UK Anti-Doping has confirmed that its computer system was subjected to a cyber attack over the weekend.
UKAD has overall responsibility for administering anti-doping in the country, and holds personal information, anti-doping records and selected medical records for the UK's top cyclists, athletes and sportspeople.
In a short statement issued on Monday, UKAD confirmed the attack but said that no data was breached.
"Over the weekend UK Anti-Doping was made aware of a cyber attack affecting our systems. We can confirm that no data has been lost or compromised," said UKAD via its Twitter account.
"We took the necessary steps to investigate and resolve the situation. No core activity, including our testing programme, has been impacted.
"We are satisfied that we have appropriate levels of cyber security in place, and we continually review our systems and measures to ensure they are of a very high standard."
According to a report published by the Independent, staff turned up at UKAD's London headquarters on Monday morning and were sent home after a meeting.
The illegal accessing of anti-doping authorities' servers was highlighted in 2016 when hacking group Fancy Bears published athlete's medical records that it had gained via the World Anti-Doping Agency's computer records.
Fancy Bears posted Therapeutic Use Exemption (TUE) certificates from a range of athletes taking part in the Rio 2016 Olympic Games, including British cyclists Bradley Wiggins, Chris Froome, Laura Trott, Callum Skinner and Steve Cummings.
The group has also previously accessed and published files stored on the computer systems of the International Olympic Committee and International Association of Athletics Federation.
It was announced in January that UKAD would receive a cash injection of £6.1million over the next two years from the British government to help fight doping.
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