A man has been arrested in connection with comments posted to the activist news site Indymedia.

The postings on January 21 included the personal details of a prominent High Court judge who had earlier that day handed down prison sentences in a landmark animal testing extremism trial.

A spokeswoman for Kent Police said the arrest was made this morning in Sheffield. No further details about the man, who has not been charged, were released. His arrest follows Kent Police's seizure of an Indymedia server in Manchester on January 22.

The two user comments that prompted the investigation were posted on Indymedia in response to a story about the jail sentences given to members of Stop Huntingdon Animal Cruelty (SHAC). Mr Justice Neil Butterfield handed down sentences of between four and 11 years for blackmail to three women and four men after they were convicted of harassing people and companies connected to Huntingdon Life Sciences (HLS).

Kent Police carried out the SHAC investigation, led by Detective Chief Inspector Andy Robbins. The receipt left with the Manchester colocation firm hosting Indymedia's server said he had instigated the seizure.

The first comment, entitled "Mr No Justice Butterfield", said: "Or plain old Neil Butterfield when you strip away his wig, gown and pompous titles. You might want to let this friend of HLS know exactly what you think about him. Just don't mention his son Sam who was killed in a taxi crash in India last year."

Sam Butterfield died on his honeymoon in January 2008. The post went on to give Mr Justice Butterfield's personal details, which were deleted by Indymedia administrators in line with the site's privacy policy.

A second commenter however reposted the information hours later on 21 January, writing: "Butterfield's details were posted on Indymedia but removed. Not before I had a chance to write them down though :-)." Indymedia administrators again removed the personal details.

The site was contacted by Kent Police on the morning of 22 January requesting that information about the posters be retained. Indymedia responded that it had configured its Apache server software not to log IP addresses in order to protect its users' privacy.

An Indymedia spokesman declined to immediately comment on today's development. Kent Police said the investigation was ongoing.

In 2004 Indymedia servers were seized as part of an FBI investigation into violent protests at G8 meetings. ®