Indian police on Tuesday launched an investigation into a deadly car blast near the historic Red Fort in the heart of the Indian capital that killed at least eight people.

In the aftermath of the blast, which happened Monday afternoon on a bustling street, authorities have shut down the Red Fort Metro station and closed the Red Fort for three days.

Several Indian states, such as Karnataka, Punjab, Haryana, Himachal Pradesh, and Jammu & Kashmir, remain on high alert.

Forensic experts are working to determine what caused the explosion at the sprawling Mughal-era Red Fort, which is a major tourist attraction in Delhi.

Police said a slow-moving car had stopped at a traffic signal and exploded just before 7 p.m. local time.

There has been no confirmation on the cause of the explosion, but the police are investigating the case under the Unlawful Activities (Prevention) Act (UAPA), an anti-terror law that allows broader powers to investigating agencies.

“Investigation is at a preliminary stage and any comment on it will be too premature,” said Deputy Commissioner of Police Raja Banthia

Modi vows ‘justice’
Indian Prime Minister Narendra Modi, who is on a visit to neighboring Bhutan, offered his condolences to the families of those killed.

“The horrific incident that happened in Delhi last evening has deeply disturbed everyone,” he said.

“The conspirators behind this will not be spared. All those responsible will be brought to justice,” he said. “Our agencies will get to the very bottom of this conspiracy,” he added.