Srinagar , India ( CNN ) -- Three men were detained in Indian-controlled Kashmir on Thursday following a deadly blast outside the Delhi High Court a day earlier , police said . Islamic extremist group Harkat-ul-Jihad-al-Islami claimed responsibility for the attack in an email to several TV news channels . `` We are questioning the owner of a cyber cafe and some other people to establish the identity of the email sender , said K. Rajendra , a police director . `` We can confirm the email was sent from Kistwar area . '' Eleven people were killed Wednesday when a bomb inside a briefcase went off outside the court , the Home Ministry said . An additional 74 people were injured . It was the second explosion outside the court complex in four months . The NIA , a security agency set up after the Mumbai terror attacks in 2008 , has joined the investigation along with police and the National Security Guard . The blast took place mid-morning , after the court opened and shortly before cases usually begin . It was a particularly busy day at the court . Wednesdays are dubbed `` public interest litigation '' days , when many members of the public arrive to put cases before judges . The briefcase was placed in front of Gate No . 5 , used by litigants and lawyers . From CNN 's Mukhtar Ahmad and Sumnima Udas .
The men are detained in Islamic -controlled Kashmir . This is the second blast outside the court complex in a day earlier . The bomb is placed in a briefcase outside a gate . The blast kills 11 and wounds 11 , Gate No . 5 says .