Thai police are looking for a man in a “blue shirt” seen in a new surveillance video for potential leads to Monday’s bombing in central Bangkok that killed at least 21 people and injured over 120, authorities said Saturday. The video was reportedly leaked to local media.

The video shows the man placing a bag on a riverside walkway, then kicking it into water Monday night, the spot where another blast occurred Tuesday, causing no casualties. Authorities are yet to determine whether the man’s action was directly linked to Tuesday’s explosion, just a day after the bombing several miles away at the Erawan Shrine.

"The thing he kicked in the water might just be garbage. We don't know yet," police spokesman Prawuth Thawornsiri said, according to the Associated Press, adding that the man is being sought for questioning.

Col. Winthai Suvaree, a spokesman for Thailand's ruling junta, reportedly said that closed circuit television (CCTV) was also being used to learn the transportation route taken by the suspected bomber. Thai officials believe the prime suspect -- an unidentified "foreign" man -- who was pinpointed with the help of CCTV footage, planted a bomb in a backpack at the Hindu shrine, one of Bangkok’s famous tourist attractions.

Police released a sketch of the suspect and issued an arrest warrant against him Thursday. Suvaree reportedly said that the sketch has been distributed to border posts.

Two suspects of the bomb attack were cleared by the Thai police late Wednesday, hours after they turned themselves in. The two men -- a Chinese tourist and a Thai tour guide -- were suspected to be linked to the blast after they were seen in the security video standing in front of the prime suspect. A woman in a black shirt who was also seen standing near the prime suspect in the footage is being sought.

On Friday, police raised the bounty for any information leading to the arrest of the suspect to 3 million baht ($85,000).