MUMBAI: One month on from the triple bomb blasts that killed 26 in Mumbai, police are still scrambling for a breakthrough, with no claim of responsibility and no arrests made.
Detectives initially said they had "good leads" over the rush-hour July 13 attacks that ripped through the city's Opera House diamond trading hub, Zaveri Bazaar gold and jewellery quarter and suburban district of Dadar.
Suspicion quickly fell on the Indian Mujahideen, a home-grown terror outfit that claimed responsibility for similar attacks in 2008 and two suspected members were questioned.
But with the trail apparently run cold and detectives refusing to discuss the case, the lack of developments mirrors investigations into a series of other recent attacks blamed on extremists and that remain unsolved.
Among the few announcements made on the probe were that the bombs contained the common fertiliser ingredient ammonium nitrate and that police had traced the owner of a scooter in which the explosives were at first thought hidden.
Reported arrests of suspects, including one in Nepal, were swiftly denied.
Fears have been expressed that heavy monsoon rains that lashed the city on the night of the attacks and ever since may have hindered the collection of forensic evidence.
Aftab Ahmed "AA" Khan, who set up the anti-terrorism squad in Mumbai in the 1990s, said the nature of last month's blasts, all in places teeming with people, was likely to be the police's main difficulty.
"It (the investigation) is going to be a laborious job. They will have to keep questioning people, sifting through all the millions of calls and hundreds of anonymous tip-offs," he told AFP.
"The kind of people who planted the bombs then went away... they're just the leg men. They're anonymous. It's impossible to identify them, whether by security camera footage or patrolling policemen...
"For a credible lead, police are going to need information from a source. They need that lucky break."
Analysts suggested that an increasing threat from unknown militants, under-investment in intelligence-gathering techniques could also be hampering the investigation.
Wilson John, a homeland security analyst at the Observer Research Foundation in New Delhi, said it was likely that individuals or groups unknown to police could be responsible.
"Many of these guys who are now participating are newcomers. They're not on the radar," he said. "I don't think anyone who has carried out these attacks in the last three years are driven by any ideology as such."
Such groups were "not terrorists in the mould of LeT (Lashkar-e-Taiba, the banned group blamed for the 2008 Mumbai attacks) or al Qaeda but they use terror tactics that are now easily available", he added.
In May, a crude device failed to explode at the Delhi High Court while the previous month about a dozen people were wounded in low-intensity blasts at a cricket stadium in the southern city of Bangalore.
In December last year, a girl was killed by a bomb at a religious bathing site in Hinduism's holiest city, Varanasi, and last September unknown gunmen attacked a tourist bus near New Delhi's biggest mosque.
Praveen Swami, associate editor at The Hindu newspaper, said the lack of breakthrough reflected misplaced priorities.
"The Indian government has been spending a lot of money on buying security equipment and weapons but very little attention has been given to the training of the police force and to upgrade their skills of intelligence-gathering," he said.
"It's a worrying fact that while the attacks are getting more and more sophisticated, our police has not been able to step up and match up to those."