At least eight people were killed and 20 injured Monday night after a car explosion near Delhi’s Red Fort, a popular tourist area.

Authorities say a slow-moving vehicle exploded at a traffic light, igniting nearby cars and rickshaws and causing a massive fire.

Police have opened a case under anti-terrorism laws but have not yet identified the cause or any suspects, saying it is “too premature” to determine whether it was a terrorist attack.

Home Minister Amit Shah and Defense Minister Rajnath Singh have pledged a full investigation, while Prime Minister Narendra Modi vowed that the perpetrators “will not be spared,” NBC News has reported.

Security has been tightened across Delhi and neighboring states, with major transport hubs and landmarks placed on high alert as investigators search for clues in one of the capital’s deadliest blasts in years.