Investigators have tracked down the Internet Protocol(IP) addresses of four different computers to the Netherlands, Saudi Arabia, France and Romania, a police officer told PTI.
"We have reasons to believe that proxy servers were used to upload offensive posts on Facebook on May 31 and June 1," he said speaking on condition of anonymity.
Efforts are on to track the actual computer from which these posts were uploaded so that the culprit could be apprehended, he said, adding "we are co-ordinating with the Indian Computer Emergency Response Team (ICERT) and hope to catch the accused soon."
17 activists of Hindu Rashtra Sena, including two minors, have so far been arrested in connection with the killing of 28-year-old Shaikh.
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In addition, around 180 people have been arrested for rioting and violence following posting of the derogatory pictures on the social networking site.
In Mumbai, an FIR was registered against unidentified persons on May 31, under Section 295 A (deliberate and malicious acts intended to outrage religious feelings of any class by insulting its religion or religious beliefs) of the Indian Penal Code and relevant sections of the Information Technology Act.
Some Hindu organisations including "Hindu Janajagruti Samiti" protested against what they called "unjustified action" against HRS activists to hide failure of the police to book the real culprits responsible for the murder.