Kent Police yesterday seized a server hosted by by Manchester-based hosting firm UK Grid and rented by the independent news collective Indymedia UK.
In a statement, the force said: "Kent Police has seized computer equipment from a company in Manchester. The company are fully co-operating as Kent Police continues with an ongoing investigation."
A spokeswoman said she was unable to provide further details "because of the sensitivity of the investigation", but said no arrests have been made. According to Indymedia, Kent Police had a warrant.
In its posting on the raid, Indymedia said it believed the server was taken in relation to postings on the the recent conviction of UK animal rights extremists. The leaders of Stop Huntingdon Animal Cruelty were handed prison sentences for blackmail on Wednesday.
Indymedia said Kent Police emailed on Thursday morning asking that a posting revealing personal information of Mr Justice Neil Butterfield, the trial judge, be removed. The collective wrote that it had already removed the information in line with its policies, and that it was unable to comply with Kent Police's request for details of the poster because it does not keep logs.
The seizure did not affect the main Indymedia site, though a few related pages were briefly offline.
UK Grid declined to comment.
Indymedia serves as a hub for activist groups on a wide range of issues. In 2004 the FBI confiscated its servers in London in investigations related to G8 protests Italy and Switzerland.
In 2005 UK police seized another Indymedia server in Bristol, again thought to be related to G8 protests. ®
The original version of this story stated that UK Grid owned the server that was seized. That was incorrect. It was owned by one of UK Grid's customers.