The tractor march by farmers protesting against the three recent agriculture laws had turned violent, leading to chaotic scenes on the streets of the national capital on Republic Day.
Thousands of protesting farmers had clashed with the police during the parade. Many of them, driving tractors, reached the Red Fort and entered the monument.
They also hoisted flags on the domes and placed a flagstaff at the ramparts of the national monument, where the national flag is unfurled by the prime minister on Independence Day.
Police had asked nine farmer leaders to join the investigation in the case on Friday, but no one turned up.