Ammonium Nitrate Fuel Oil Found In Delhi Red Fort Blast. What Is It?

An unspecified amount of ammonium nitrate fuel oil – combined with a detonator, possibly manually triggered – was used in the bomb that exploded near Delhi's Red Fort last night, sources told NDTV Tuesday morning, pointing to a preliminary report.

Nine people were killed and 20 injured in the explosion, which came hours after an inter-state crackdown on a terror module run by Pakistan-based terrorist group Jaish-e-Mohammed.

The bomb was packed into a white Hyundai i20 with Haryana number plates that was re-sold a few times, including once to a man from Jammu and Kashmir's Pulwama, possibly to confuse investigators – that entered Delhi via the Badarpur crossing and was then parked near the Red Fort for three hours.

First photos of the suspected terrorist, a Dr Umar Mohammed, have emerged, showing him sitting inside the car while it was parked; from available CCTV footage, it appears Mohammed did not leave the car at any time, likely to make sure the explosives weren't discovered.

READ | 1st Pic Of Delhi Blast Suspect Surfaces, He Parked Car Near Red Fort

At 6.52 pm, Delhi Police chief Satish Golcha told reporters, the car pulled up to a red light at Subhas Marg, a crowded part of old Delhi, and within seconds, it exploded. The intensity of the blast was such that 22 nearby vehicles also caught fire, and body parts were thrown around, eyewitness told NDTV.

The explosion

Ammonium nitrate – formula NH4NO3 – is an odourless, white crystalline chemical widely used as a fertiliser but is also a powerful oxidiser that, under the right conditions, can cause a powerful explosion resulting in fires that burn at high temperatures for sustained periods.

Ammonium nitrate by itself is not considered an explosive.

Chemical formula for ammonium nitrate.

It needs to be mixed with an secondary substance – in this case, fuel oil, which is a petroleum-based product – and triggered by an external detonation that gives off immense heat to explode.

In fact, it can be mixed with almost any kind of volatile substance. But the quality is important; pure NH4NO3 is chemically and thermally stable, meaning it requires that external detonation.

And a stronger initial blast is more likely to result in a larger and more stable explosion.

When combined with fuel oil, it becomes ammonium nitrate fuel, or ANFO, which is a commonly used bulk explosive in the construction and mining industries. It is popular because it is an inexpensive and simple explosive to manufacture and, if handled correctly, safe to store.

Its explosive power is another reason it is popular.

Legal status in India

Sale and possession is supposed to be tightly controlled in India.

Under rules framed in 2012 (and amended in 2021), "any combination with more than 45 percent of ammonium nitrate by weight, including emulsions, suspensions, melts or gels (with or without inorganic nitrates) shall be called an explosive".

In simple terms, AN is a salt consisting of one ion each of ammonium and nitrate.

As a result, manufacture, storage, and use requires licences from the Petroleum and Explosives Safety Organisation, and unauthorised individuals cannot purchase or possess ANFO.

How the terrorists managed to secure such large quantities of ammonium nitrate and other explosive substances used is one of the biggest, if not the biggest, question investigators need to answer.

A terrorist favourite?

For the above reasons, ANFO has been used in several terrorist attacks worldwide, the most famous of which was probably the bombing in Oklahoma in the United States in April 1995.

On that occasion, 5,000 pounds (nearly 2,300 kg) of ANFO was loaded into a truck parked under the Alfred P Murrah Building, which housed federal administrative offices, in Oklahoma City.

Carried out by anti-government extremists Timothy McVeigh and Terry Nichols, the attack killed 168 people and injured over 900, and the blast destroyed or damaged over 300 nearby buildings.

Aerial view of the devastated Oklahoma City building. Photo: FBI

The monetary damage was estimated at $US652 million.

ANFO was also used in a 1970 bombing in Wisconsin; in August that year four men bombed Sterling Hall on the campus of the University of Wisconsin-Madison to protest the US' involvement during the Vietnam War. The bombers packed 2,000 pounds (around 910 kg) into a stolen Ford van.

It exploded at 3.42 am, killing one person and injuring three others.

While fatalities were restricted because of the hour of the bombing, the intensity was such that pieces of the van were found on the roof of an eight-floor building three blocks away.

ANFO has been used in terror attacks in India too.

In 2012 a series of low-intensity blasts hit Pune's busy Junglee Maharaj Road. Recovered explosive residue tested positive for the substance. In that case, however, luck was not on the bombers' side; four of the six devices failed to explode and no deaths were reported.

The biggest blast in the Mumbai 2011 attack was at Prasad Chambers in the Opera House area.

ANFO was also used in Mumbai a year earlier. The July blasts – three, coordinated explosions at Opera House, Zaveri Bazaar, and Dadar West – killed 26 people and injured 130 others.

Apart from these, ANFO, or ammonium nitrate variations, were also used in the bombing of the US embassy in Beirut in Lebanon in 1983 and the British consulate in Istanbul, Turkey, in 2003.

The Faridabad connection

Over 300kg of the substance was recovered Sunday from two residential buildings linked to another medical professional – a Dr Mujammil Shakeel who worked at the Al-Falah Hospital in Faridabad.

NDTV Explains | How Dangerous Is Ammonium Nitrate, Really

Shakeel and a third doctor, Adil Ahmed Rather, were arrested hours before the Red Fort Blast – Shakeel from Faridabad and Rather from Uttar Pradesh's Saharanpur.

Sources told NDTV Mohammed was part of that terror module; he panicked after the arrests and seizure of the ammonium nitrate, part of 2,950 kg of other explosives substances found.

READ | Panicked Doctor Triggered Delhi Blast? Suicide Attack Angle?

Sources also said he escaped arrest and, left with no option, triggered the Red Fort attack plan.

The Faridabad arrests and seizures have also focused spotlight on apparent new tactic being used by terrorists – to pose as medical practitioners, real or otherwise, to gain people's trust.

Apart from Shakeel, Rather, and Mohammed, a fourth doctor – a woman – has also been arrested.

READ | Ammonium Nitrate To Ricin: Poison, Terror Attacks And The Doctors Behind

At least one other doctor has been arrested on terrorism-related charges this week – Gujarat-based Ahmed Saiyed – was detained with ingredients to make ricin, a deadly toxin.

What now

The Red Fort blast is now being probed as a terror attack, with Delhi Police invoking sections of the stringent anti-terror law, the Unlawful Activities (Prevention) Act (UAPA), and sections of the Explosive Substances Act, as well as charges of murder and attempt to murder.

READ | White Collar Terror Ecosystem In J&K, 2,900 kg Of IED-Making Material

Meanwhile, police and intelligence agencies raided locations across J&K (Srinagar, Anantnag, Ganderbal, and Shopian) as well as Faridabad over the past few days to uncover a worrying white-collar, terrorist ecosystem operating involving radicalised professionals, many of whom are doctors.

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