Hours after receiving the preliminary forensic report on the blast, Singh told reporters that shrapnel was used in the blast to maximise the impact and casualties. Officials had yesterday claimed the blast was carried out using pentaerythritol tetranitrate (PETN), which is a plastic explosive.
A high-intensity explosion at the Delhi High Court killed 12 people and injured more than 75 others.
Meanwhile, a man has been detained from Balrampur district in Uttar Pradesh on the basis of a sketch of two suspects released by the Delhi police on Wednesday. However, reports are claiming that new sketches could be released soon.
Earlier in the day, security officials traced Harkat-ul-Jehadi Islami (HuJI) e-mail claiming responsibility for the blast to a cyber café at Kishtwar in Jammu and Kashmir.
Cyber cafe owner Mehmood Khawja was detained along with two others for questioning in connection with the Delhi blast, police officials said.
They are being interrogated in connection with the e-mail, they said.
One of the detained persons has been identified as Khalid.
Policemen in plainclothes have been deputed outside the cafe in Kishtwar town and are keeping a close watch on the movement of people.
DGP Kuldeep Khoda earlier said, "We are investigating the e-mail link from Kishtwar district in connection with the Delhi blast".
"We are probing whether there is any link or not with the e-mail from Kishtwar", he said, adding police are working on it.
Jammu and Kashmir Police had conducted raids after it became known that the e-mail, purportedly by Harkat-ul Jehadi Islami, had been sent from a cyber cafe in Kishtwar.
The National Investigation Agency zeroed in on Global Internet Cafe at Malik Market in Kishtwar as the place from where the e-mail was sent.
The e-mail was reportedly sent by the Bangladesh-based terror outfit from id: harkaruljihadi2011@gmail.com.
NIA chief SC Sinha said, "HuJI is a lethal group... we take the mail very seriously.”
The e-mail states, "We owe the responsibility of today's blasts at High Court Delhi... our demand is that Afzal Guru's death sentence should be repealed immediately else we would target major high courts and the Supreme Court of India."
Mohammed Afzal Guru is on death row for his role in the attack on the Parliament in December 2001.
The National Investigating Agency (NIA) has taken over the investigation and is probing all angles.
A powerful bomb went off outside the Delhi High Court at 10.17 am on Wednesday. The blast occurred between Gate No 4 and 5 of the Delhi High Court when around 200 visitors, mostly litigants, were waiting in queue to get passes to enter the court premises on a busy PIL day. Around 200 people are said to have been at the spot at the time of the blast. The bomb is believed to have been placed in a briefcase and left near gate number five of the court.
Severed limbs and pieces of flesh lay strewn on the ground where there were pools of blood after the deafening explosion that dug a small crater outside the reception area.
Home Minister P Chidambaram confirmed in Parliament that the blast was a terror attack. However, the module behind the attack is yet to be identified. He said that the perpetrators of the blast would be brought to justice.
Delhi Police have in the past arrested several HuJI militants from the national capital.