IEDs found in a Seemapuri house on Thursday and at the Ghazipur market last month were prepared with the intention of carrying out blasts at public places across the city, according to Delhi Police Commissioner Rakesh Asthana.
Such activities are not possible without local support, the Delhi police chief said on Friday.
A day after the bag containing the IED was found in northeast Delhi's Old Seemapuri area, the police have stepped up security and deployed additional personnel there, officials said.
The improvised explosive device (IED), weighing 2.5 to 3 kg, was later defused while the owner of the house and a property dealer are being interrogated by the police, they said.
Talking to the media, Asthana said an IED was recovered in Ghazipur on January 17 and a similar IED was also recovered and neutralized in Old Seemapuri on Thursday.
"According to the probe, these IEDs were prepared with an intention to carry out blasts at public places. Such activities are not possible without local support," he said.
The special cell and other teams are investigating the case, he said, adding that they are probing forward and backward linkages.
"We are trying to preempt every such incident in Delhi and expose any local and foreign network," he added but refused to divulge any other detail.
A senior police officer said around 400 people were vacated from nearby buildings after the "suspicious" bag was found.
"We have stepped up the security in the area. We have put up barricades and sealed the house. The crime scene has been preserved.
"The local police had also conducted the verification of tenants in the area as part of security measures ahead of the Republic Day. A local enquiry has also been conducted by the local police," the officer said.
A special cell team has also retrieved the footage of all the CCTV cameras installed in and around the building where the suspicious bag was found.
The footage from the cameras is being analysed, the officer said.
The mother of house owner Aashim alleged that the police have taken him in their custody, while his wife said they had rented out the floor, where the explosives have been found, to two persons a couple of months ago.
During interrogation, the owner of the house told the police that he had taken the documents of two people while giving the house on rent.
However, the documents are yet to be recovered by the special cell unit probing the case, another senior police officer said.
NSG sources had said the explosive is suspected to be a mix of ammonium nitrate and RDX but a forensic lab will examine it in detail.
With this explosive having similarity with the one recovered from the Ghazipur flower market ahead of Republic Day last month, the police believe that both these cases might be linked to the same people.
According to an official, investigation into the Ghazipur flower market case led the police to receive a tip-off about the explosive in Old Seemapuri.
No sooner was the information received in the afternoon, special cell teams dashed to the site. NSG officials and the Forensic Science Laboratory team were also rushed to the spot.
The officer said, "When our team went to the house, it was vacant. The bag was found there and we immediately informed the NSG."
"The suspects have managed to escape. We suspect the explosive recovered from Old Seemapuri has been made by the same persons who placed IED at Ghazipur flower market last month," the officer said.
The IED was picked up by the NSG bomb disposal squad from the second floor of the building. Security has been beefed up and the area cordoned off.
The IED was destroyed using a water disruptor, an NSG officer said, adding that all pieces of evidence have been handed over to the Delhi police.
In January, an IED stuffed with RDX and ammonium nitrate was found inside an unattended bag at the Ghazipur flower market and was defused.
