Investigators trying to string together bits of evidence in the serial low-intensity blasts in the city have hit a hurdle as some CCTV cameras at the explosion sites have been found to be non-functional.

The CCTV cameras installed at Dena Bank, McDonald's and Bal Gandharva traffic square, near where the explosions occurred, have not yielded any clue so far and some of them were non-functional, sources in the investigative agencies said on condition of anonymity.

Sources said the Maharashtra ATS, city Crime Branch and the NIA are looking for clues from the two bicycles as two of the four coordinated blasts on Wednesday night occurred in their front carriers.

Explosives were strapped on these bicycles which appear newly purchased and investigators are trying to locate the shop from where these were bought in order to nail the perpetrators.

As reports said a black sticky substance with ammonium nitrate was used in the explosions, forensic experts are also trying to ascertain the concentration of explosives in the devices to zero in on the likely group behind the blasts.

According to sources, different terror groups use varied concentration of explosives in their 'signature bombs'.

Reports have said battery operated detonators with digital timers could have been used to trigger the blasts. Dayanand Patil, the only person injured in the blast at Bal Gandharva Theatre square, is being questioned by the police as to how the explosive found its way into his carry bag.
Sources said Patil, who sustained minor injuries, was not being treated as a suspect in the case. Patil, who hails from nearby Urali Kanchan village and used to commute daily to Pune for tailoring work, is in hospital where his statement is being recorded, they said.

Patil has told the police that he had visited the dharna by Anna Hazare's India Against Corruption and somebody kept the explosive in his carry bag. The explosion occurred when he tried to open a box in which the explosive was kept.

His wife, Satyakala, was also being questioned by police, sources said. Police have registered an offence against 'unknown persons' under sections 307 (attempt to murder), 427 (mischief causing damage), 120 B (criminal conspiracy) and relevant sections of Unlawful Activities Prevention Act and Explosive Substances Act.

Pune Commissioner of Police Gulabrao Pol had on Wednesday said as very low-intensity explosives were used in the blasts, it did not appear to be the handiwork of terrorists and could be an act of mischief.

However, Union Home Secretary R.K. Singh said in Delhi that terror angle could not be ruled out as the blasts occurring minutes apart were a coordinated act.

Meanwhile, activists of India against corruption (IAC), who have been staging a dharna just opposite the Bal Ghandharva Theatre, said they would call it off temporarily in response to a directive by police for security reasons. Meanwhile, life in the city and busy Jangli Maharaj (JM) road, where the four coordinated blasts occurred, is normal.

Barring the blasts sites which have been barricaded by police, people could be seen moving as usual on the occasion of Raksha Bandhan. Maharashtra Home Minister R.R. Patil, who visited the blast sites, also held a meeting with top police officials this morning to review the situation and take stock of the probe.