Sources said some eye-witnesses have told them that a man clad in a white shirt and carrying a briefcase was seen in a queue in front of the reception of the high court complex on Shershah Road just before the explosion.
Investigators said they were yet to ascertain whether there was a timer in the device.
"It may be possible that the bomb planter could not escape from the spot before the explosion took place. If there was a timer, he could have had ample time. There is also a possibility that the suspect could not manage to escape from the spot," a senior police official said.
Mahender, an eye-witness who had come to the high court for a hearing, claimed, "One person clad in a white shirt came with a briefcase and stood in the queue after which a bomb exploded within seconds."
"People were standing in the line to get their passes to enter the court premises. I did not know the process to get into the complex as this is the first time I was coming for a hearing at the high court," he said.
"When I was standing in the line along with my friend, one person came in a white shirt with a briefcase in his hand and within seconds there was a blast. I could not see anything," Mahender said.
He said he sat on the floor after the blast took place only to see that the person who was accompanying him was injured.
"I asked him to go out and a policeman came and helped us immediately. The police reached the spot within minutes and helped people," he said.
