Delhi Police Commissioner Dr K K Paul says Sunday evening's blasts at the Satyam and Liberty cinema halls, that left one dead and over 60 people injured, were low-intensity blasts.
No shrapnel or chemicals were found from the two theatres, the police commissioner said.
The blasts went off within a space of 10 minutes at the two cinema halls, which were screening Sunny Deol's controversial film Jo Bole So Nihal that was withdrawn from cinemas in Punjab last week after protests against the movie.
One person was injured in a blast in Delhi on Monday morning.
Dr Paul told rediff.com on Monday, "Our officers have been on the job throughout the night to collect evidence. The nature of injuries received by people indicate that they hurt themselves as they rushed out in panic or because debris fell from the theatres' false ceilings."
"Are you looking into the Punjab angle?" this correspondent asked the police commissioner.
"Naturally. We have a description of the people who could be behind the blasts. But it is difficult to say how the explosives were carried into the two halls. We have now tightened the security at cinema halls after the incident," he said.
Meanwhile, Union Home Minister Shivraj Patil has asked the Delhi police to be "extra vigilant" in the wake of the three bomb blasts in the capital.
While the police was maintaining a "close vigil", he said, "yesterday had its own significance since the UPA government had assumed office on this very day a year ago and such occasions are used by undesirable elements to create law and order problems."
On Monday, a Lashkar-e-Tayiba militant was arrested in Delhi, police sources said.
Mohammad Irshad was nabbed in Safdarjung area by the Special Cell, which is investigating the blasts, the sources said.
However, it was not clear whether he was involved in the explosions.
Additional reportage: PTI