As Indian police investigated a deadly car explosion in New Delhi, relatives awaiting news of their loved ones who may have been injured during the blast gathered outside a hospital.

Some expressed frustration, stating they were struggling to find information on their loved ones.

Indian Prime Minister Narendra Modi said the perpetrators behind the explosion near the historic Red Fort "won't be spared" and investigators would “get to the bottom of this conspiracy".

Indian police were investigating the explosion under an anti-terrorism law, officials said Tuesday, as forensic experts worked to determine the cause of the blast.

The explosion occurred Monday, killing at least eight people and injuring several others.

Senior police officials told The Associated Press that a case was registered under the Unlawful Activities (Prevention) Act, India’s main anti-terrorism law, which allows broader powers to investigating agencies to detain suspects.

The officials spoke on condition of anonymity because of the sensitivity of the case.

Police said the explosion was believed to have originated from a Hyundai i20 car that had stopped at a traffic signal.

Nearby vehicles were badly damaged, and photos showed shattered windows, twisted metal and flames engulfing several cars.

Police were trying to trace the car’s owner.

There was no immediate information about the occupants, who were believed to have been killed.