Indian police are probing a deadly car blast in the capital Delhi under a stringent law used to fight “terrorism”, television channels reported on Tuesday, citing a case registered by the police.

The law, called the Unlawful Activities (Prevention) Act, is India’s main anti-terrorism law. It is used to investigate and prosecute acts related to “terrorism” and activities that threaten the sovereignty and integrity of the country.

Reuters could not immediately verify the reports.

The explosion near the historic Red Fort on Monday evening killed at least eight people and injured 20, a rare blast in the heavily guarded city of more than 30 million people, sending several states and key facilities into high alert.

Federal Home Minister Amit Shah said on Monday “all angles” were being investigated and security agencies would come to a conclusion soon.

Police said a slow-moving car which stopped at a traffic signal exploded just before 7 p.m. (1330 GMT). Nearby vehicles were also badly damaged.

The explosion left behind mangled bodies and the wreckage of several cars on a congested street near a metro station in the old quarter of Delhi.

The Red Fort, known locally as Lal Qila, is a sprawling, 17th-century Mughal-era edifice melding Persian and Indian architectural styles, and is visited by tourists throughout the year.

The prime minister also addresses the nation from the fort’s ramparts every year on August 15, India’s independence day.