Manhattan bomb: What clues are there for investigators?

Manhattan bomb: What clues are there for investigators?

What do we know about the explosives?

With New York's Mayor confirming that Saturday night's blast in Manhattan was "an intentional act", investigators are now urgently trying to determine the motivation for the bombing and who might be responsible.

The discovery of a second suspicious device, just a few streets away from the first, could offer vital clues in the ongoing investigation.

Law enforcement sources have confirmed that the second device was contained within a pressure cooker and had wires attached to a mobile phone.

If confirmed that the second device is connected to the first bomb, it should provide valuable forensic evidence, as the device did not detonate and has now been removed for detailed analysis.

Robot probes suspect device near NY blast

As well as examining it for fingerprints and other DNA evidence, investigators might also be able to trace the pressure cooker back to the store it was bought from.


A second confirmed device, just a short distance from the first, would also point to a more co-ordinated style of attack and raise concerns that other devices might still be out there.

Police are examining CCTV and other footage from around the scene of the bomb blast.

One particular sequence of video shows a person at the spot where the bomb detonated, just a short time before the explosion.

Robot probes suspect device near NY blast

Pressure cooker bombs have been used in past terrorist attacks, most notably the Boston marathon bombing in 2013.

Two pressure cooker bombs exploded within seconds of each other near the finish line, killing three people and injuring more than 260 others.

Pressure cooker devices have been used in attacks in the West more frequently, as they are relatively easy to construct, but still potentially deadly in nature.

CCTV catches Manhattan blast

Terrorist organisations, including IS and al Qaeda, as well as anarchist groups, have widely published documents showing followers how to build this type of bomb.

More sophisticated improvised explosive devices, like the bombs that killed 52 people and injured almost 1,000 in London on 7 July 2005 are more rare.

Those bombs used hydrogen peroxide and required a greater degree of expertise in their construction and handling.

Other past devices have used ammonium nitrate fertiliser as their base ingredient but authorities in the US and other countries have now adopted better monitoring processes to help ensure they are alerted when individuals try to bulk buy ammonium nitrate or hydrogen peroxide.

Debris seen at site of Manhattan blast

Terror groups are now actively encouraging supporters to adopt less sophisticated devices to get around those safeguards.

As this stage, publicly at least, authorities in New York have still to reveal a possible motivation for Saturday night's attack.

The top priority for investigators is the hunt for the bomber - or bombers - before they plant any further devices.