Indian authorities claimed on Sunday that a deadly car blast in New Delhi earlier this week was an attack carried out by a “suicide bomber”, announcing the arrest of an accomplice.

The National Investigation Agency (NIA), the country’s counter-terrorism body, said the attacker and the second suspect were both from India-occupied Kashmir, where police have carried out sweeping raids in recent days.

Announcing “a breakthrough” in the investigation, the NIA said it had arrested Amir Rashid Ali, describing him as an accomplice of the “suicide bomber” under whose name “the car involved in the attack was registered”.

He had come to Delhi to “facilitate the purchase of the car which was eventually used as a vehicle-borne Improvised Explosive Device (IED) to trigger the blast”, the counter-terrorism agency said in a statement.

It identified the car’s driver as Umarun Nabi, a resident of occupied Kashmir who was an assistant professor in general medicine at a university in the northern state of Haryana.

The explosion on Monday took place near a busy metro station close to the landmark Red Fort in the capital’s Old Delhi quarter, where the prime minister delivers the annual Independence Day address.

A hospital official said the blast killed 12 people. It was unclear whether Nabi was included in the toll. The NIA’s statement said the attack “claimed 10 innocent lives and left 32 others injured”.

The NIA claimed it had seized another vehicle belonging to Nabi.

Indian Prime Minister Narendra Modi called the attack a “conspiracy”, and his government vowed to bring the “perpetrators, their collaborators and their sponsors” to justice.