Red Fort blast: Early probe points to military-grade explosives - How deadly are PETN, RDX, ANFO?

Delhi blast

The Investigators are still unsure exactly what explosive or chemical caused Monday’s deadly car blast near the Red Fort. Forensic teams and the National Security Guard’s (NSG) explosives unit have collected evidence and begun testing, but no final report has been shared yet.

However, early findings suggest the device may have used powerful, military-grade explosives, given the scale of the damage and the number of casualties.

Teams working at the blast site have recovered about 42 exhibits so far. These include parts of the exploded Hyundai i20 which include the tyres, chassis, CGC cylinder, parts of the bonnet, and various fragments and powder traces.

All material has been sent to labs for chemical and microscopic testing. As per the investigators, these samples will be crucial in identifying the exact explosive used and the method of detonation. The NSG’s explosive experts are also examining the wreckage and will send their technical assessment to the probing agencies.

What all was used for the explosion?

According to a report by TOI, investigators have asked forensic teams to check for traces of PETN, semtex or RDX, as well as ammonium nitrate fuel oil (ANFO) and detonator components.

PETN (pentaerythritol tetranitrate) is a powerful explosive often found in plastic explosives like semtex. It is highly energetic, effective in small amounts, and its colourless crystal form can be hard to spot. PETN detonates under shock or heat and does not need added metal fragments to cause severe damage, the blast energy from the explosive itself is enough to destroy a vehicle. Because of its strength and low detectable profile, it has been used in past terror plots.

RDX is another military-grade explosive known for strong blast power and has been linked to some past attacks.

ANFO, a mixture of ammonium nitrate and fuel oil, is cheaper and easier to obtain. It makes a powerful, supersonic shock wave when detonated and is commonly used in large improvised explosive devices.

Officials note that mixed charges, for example, combining PETN or RDX with ANFO, have been used in past incidents to increase destructive effect. In the 2011 Delhi High Court blast, initial forensic opinion pointed to a mix of ammonium nitrate and PETN, though later statements mentioned RDX.

Battery-powered trigger suspected

Apart from explosive residues, investigators are also focusing on how the device was set off. Initial investigations suggest a proper detonation circuit may have been built into the car. Small electronic parts found at the scene point to the possible use of an ordinary watch and button batteries to trigger the device. Such simple circuits can act as timers or switches, making them useful in improvised bombs.

According to the officials, while preliminary assessments point to certain types of explosives, final confirmation will come only after laboratory analysis of the collected samples.

Authorities say they expect clearer results in a few days and will continue piecing together the technical, forensic and electronic evidence to determine exactly what caused the blast and how it was assembled.