The Serious Organised Crime Agency website has been taken offline after becoming the target of a cyber-attack, the agency said.
Soca confirmed that its site, soca.gov.uk, suffered a distributed denial of service (DDoS) attack.
A spokesman said the site was taken offline at 10.30pm on Wednesday, but the attack did not pose a security risk to the organisation.
Soca has recently closed 36 websites believed to be selling stolen credit card information.
"We took action to limit the impact on other clients hosted by the [same] service provider," the spokesman said.
In June last year the agency website went offline for several hours and LulzSec said it was behind the denial of service.
A trial at Southwark crown court will take place later this year in connection with the earlier attack.