Asked whether the blast was a terror strike, Singh said "it had all the makings of an Improvised Explosive Device(IED) set up by a terror group."
Singh said 45 people were injured with some eyewitnesses saying some of the injured were in a critical condition.
Special Commissioner Dharmendra Kumar told reporters the bomb was apparently kept in a briefcase.
It was the second blast in four months outside the High Court premises. No one was injured in the previous explosion on May 25.
"We are investigating how the brief case was placed there It is not a controlled area. There were lots of people," said Kumar.
Delhi police suspected use of potassium nitrate in the bomb.
Court proceedings were adjourned till 2 pm. The main court premises where all the courtrooms are housed have been evacuated.