Suicide bomber suspected, CCTV footage holds key

What has aided this theory is the discovery of a headless body with a circuit at one of the blast sites, he said.
But Maharashtra Anti-Terrorism Squad (ATS) Chief Rakesh Maria said it was too early to say whether a “human bomb” was involved.

Preliminary investigations have revealed that the bombs may have been a deadly mix of ammonium nitrate, explosive TNT, oil and ball bearings.

According to sources, investigators are also in possession of crucial footage recorded by CCTV cameras installed at Opera House and Dadar — the third blast site was Zaveri Bazar. The CCTV cameras hold the key to the probe and may help in identifying those who planted the explosive devices.

The sources said forensic experts had collected traces of ammonium nitrate, fuel, TNT and ball bearings from the blast sites which may lead to the perpetrator of the terror attack that killed 18 and injured 113; 23 persons are said to be in a serious condition.

It is the worst terror attack in India after the November 2008 strike that left 166 dead.
Sources said that evidence from the sites suggested that battery power was used to trigger the blasts for which at least seven improvised explosive devices (IEDs) were used.

Ammonium nitrate, a chemical compound that enhances the combustibility of explosive devices has been a favourite of terrorists. The chemical is used in a fertiliser.
Mixed with fuel, like diesel, petrol or kerosene, and powered with booster charge and detonator, the cocktail turns into a bulk explosive. Pieces of metals, which can be nails or ball bearings, are added for shrapnel effect.

When the device is detonated, the metal pieces act like missiles.
Home Secretary Singh told reporters in New Delhi that the IEDs were “not crude” and indicated that they were prepared with “some level of sophistication”.

Though the ammonium nitrate used in the explosions has been confirmed by officials, investigators said they faced difficulty in ascertaining the exact composition as rains had washed away the evidence.

In Kabutarkhana Dadar West, the IED was reportedly placed on top of a bus shelter. This was a low-intensity blast which injured 10 people.

The IED at Opera House was planted below a loose slab and concealed under garbage. This blast was quite powerful, killing 11 and injuring 73.

In Zaveri Bazar the explosive device had been placed near a motorcycle concealed under an umbrella. In this blast six people died and 50 were injured.

Union Home Minister P Chidambaram who visited the blast sites, made it clear that it was too early “to point a finger at any one group”.

All groups “hostile to India” are on the “radar”, he said. But the Indian Mujahideen (IM) is emerging as the prime suspect. Three IM suspects arrested three days ago are being grilled by the National Investigation Agency (NIA) and the ATS of the Mumbai police.

The investigation is being conducted by the Maharashtra ATS and the Crime Branch, Mumbai Police, assisted by the NIA, the post-blast probe unit of the NSG and four teams from the Central Forensic Science Laboratories. The NIA has three teams lead by an inspector general assisting the investigations.