Imphal, Dec 27 (ANI): At least four people were injured in a grenade blast on Friday in Imphal, Manipur. The blast took place at around 5.30 pm when an unidentified person hurled a grenade in front of an office 'Angels Digital Media Service'. The injured, who were inside the shop at the time of blast, sustained minor injuries. Security personnel rushed at the site and investigation is underway. No group has claimed responsibility for the blast yet. On December 21, three people were killed and four sustained injuries in a bomb explosion in Imphal. Manipur is one of the seven states that make up India's remote northeast.