Home Ministry officials said the nature of explosives used in the blast was not known immediately and the post-blast investigative teams of the NIA and NSG have picked up leads from the spot.
All states have been asked to take precautionary measures and step up vigil in the wake of the blast in the national capital, the officials said.
"Rains did not have any affect on post-blast probe and evidence has not been damaged," a Home Ministry official said.
He said the perpetrators considered the High Court as an easy target and that is why two successive blast have occurred here.
The last explosion, a low intensity one, occurred outside the same court on May 25 this year.
The explosive device was suspected to have been kept in a briefcase outside the High Court compound between Gate No. 4 and 5 and went off at around 10.15 AM when 100 to 200 litigants were waiting to get passes to enter the premises. Some lawyers were also present at that time.
Condemning the "terrorist attack", Home Minister P Chidambaram said the probe into the second bomb blast outside Delhi High Court in four months has been handed over to the National Investigative Agency(NIA).He said the bomb was suspected to have been kept in a briefcase.
Maharashtra Chief Minister Prithviraj Chavan reviewed the security situation in Mumbai and the rest of the state following the Delhi blast.
Chavan has instructed guardian ministers to remain present in their respective districts on Anant Chaturdashi, when idols are immersed at the end of the 10-day Ganesh festival, and monitor security arrangements.