Indian security agencies are investigating a deadly explosion on Monday in New Delhi that killed at least eight people as a possible terrorist attack, raising concerns that regional tensions could spiral again.
If proven to be a deliberate attack, the blast near a subway station during the busy evening rush hour in the old city would be the deadliest in India’s capital since a briefcase bombing at the gates of a local court killed over a dozen people in 2011.
Officials have said that investigators are keeping all angles open, although the police indicated Tuesday that they are looking into whether it was a terrorist attack.
India frequently accuses Pakistan of being behind terrorist attacks on its soil, saying that they are orchestrated by groups operating from sanctuaries across the border.
A deadly terror attack this spring in the restive Kashmir region that killed 26 led to days of clashes between India and Pakistan. At the time, the government of India’s prime minister, Narendra Modi, issued a warning that it would treat any future terror attack on its soil as an “act of war.”
While violence has continued to mar the restive Kashmir region, India’s major cities have remained relatively safe.
Mr. Modi, who arrived in Bhutan for an official visit on Tuesday, said he had followed the case with investigating agencies overnight.
“The conspirators behind this will not be spared,” Mr. Modi said. “All those responsible will be brought to justice.”
Raja Banthia, a senior police official in New Delhi, told reporters at the blast site early on Tuesday that the police had filed a case that included sections of the Unlawful Activities (Prevention) Act, a law usually used for investigating terror cases.
“The investigation is in a very preliminary stage,” Mr. Banthia said.
Late on Monday, Amit Shah, India’s home minister, said that investigators were pursuing “all angles.”
On Tuesday, Mr. Shah is meeting top police officers, who are expected to provide him with details of the investigation so far, including the progress of lab tests on evidence found at the scene.
Monday’s blast came at the end of a day when Indian police said they had busted an “interstate and transnational terror module.” They said they confiscated several weapons and a large amount of bomb-making material that the police said was linked to Jaish-e-Mohammed, a Pakistan-based group long accused of attacks in India.
Police in Jammu and Kashmir, part of a region that India and Pakistan dispute, said they had followed leads from the restive valley to towns outside Delhi, where they arrested half a dozen suspects and confiscated over 6,000 pounds of material that could be used to make bombs, including explosives, chemicals, electronic circuits, and remote controls.
The police have not commented on Indian media reports suggesting the explosion could be related to the same suspected terror cell.
The Red Fort area, where the blast occurred, is a crowded part of the capital that leads to the bazaars and other historic sites of the old city.
Leeladhar Vishvkarma, 34, a cook from central Madhya Pradesh State who had come to Delhi in search of work, described the immediate blast as “earthshaking.”
“After the main blast, some smaller blasts took place in other vehicles,” he said. “People died inside and outside the vehicles.”
