Ammonium nitrate was again used in Saturday's blast in south Delhi's Mehrauli area that killed a boy and left nearly two dozen people injured.
Officials said Ammonium nitrate was accompanied with one-and-a-half inch nails, which acted as shrapnel leading to injuries.
The packing of explosive was very loose, thus making it a low-intensity explosion.
The same explosive material was used in the five serial blasts that shook the national capital on September 13, leaving 24 people dead and many others injured.