The National Investigative Agency (NIA) is assisting in the probe into the explosion outside the Delhi High Court in which at least nine people were killed and 45 injured.

"An NIA team has already reached he blast site. Another will be reaching soon," NIA Director Prakash Mishra told reporters here. He said the agency would assist Delhi Police in the investigations.

Personnel of the National Security Guard (NSG) have also reached the spot, officials said.