New Delhi: Investigators have collected over 40 samples, including two cartridges — one of them containing live ammunition — and traces of two different types of explosives from the blast site near Delhi’s Red Fort, officials said on Wednesday.

According to forensic experts, preliminary analysis indicates that one of the explosives appears to be ammonium nitrate. “The second explosive sample is believed to be more powerful than ammonium nitrate. Its exact composition will be confirmed after detailed forensic examination,” an official stated.

The Forensic Science Laboratory (FSL) team recovered the cartridges during a thorough inspection of the scene. A high-intensity explosion had ripped through a slow-moving vehicle near the Red Fort traffic signal on Monday, killing 12 people.

Earlier the same day, police recovered 360 kilograms of ammonium nitrate from Faridabad as part of the investigation. Two individuals — Dr Muzammil Ganaie and Dr Shaheen Sayeed, both associated with Al Falah University — were arrested in connection with the case.

Officials said the FSL has formed a special team to analyse the collected evidence and determine the precise nature of the explosives used. “The team has been directed to expedite the examination and submit the report without delay,” they added.

The laboratory has been operating round the clock since the blast as investigators continue to piece together how the explosives were assembled and detonated.