Thai police

Authorities found a nitrogen tank containing the vials in the man's bag when he was crossing the border at the northern Thai town of Nong Khai.

Police said the man confessed that the semen was bound for a fertility clinic in the capital of Laos - Vientiane.

Laos has seen a boom in commercial surrogacy after neighbouring Thailand and Cambodia banned the practice.

The semen was collected from Chinese and Vietnamese men, police said.

Authorities are confident that the two men in custody, identified as Adem Karadag and Mieraili Yusufu, are the culprits responsible for the bombing at the Erawan Shrine on Aug. 17 that killed 20 people and injured more than 120, said National Police Chief Somyot Poomphanmuang. 

Police are seeking at least 15 other people they believe are tied to the case.

Authorities will seek an arrest warrant soon for a man who shared an apartment with a suspect who was arrested a week ago when a police raid found bomb-making materials in his room, said national police spokesman Lt. Gen. Prawut Thavornsiri, adding that the man's nationality was unknown.

The arrested man, whom Thai authorities have identified as Adem Karadak, was brought to court Saturday to obtain permission for his detention to be extended. 

However, he denied placing the bomb, as other clues pointed increasingly to a link with the trafficking of an ethnic group from China via Thailand.

Thai authorities said the suspect's fingerprints also matched those on a bottle of bomb-making material found in an apartment that was raided this past weekend.

The bombing took place two weeks ago.

National police spokesman Prawuth Thavornsiri said he was certain the two were part of a group responsible for the Aug. 17 blast at the Erawan Shrine in central Bangkok that killed 20 people, more than half of them foreigners.

National police spokesman Lt. Gen. Prawut Thavornsiri said the two men "were most likely not involved."

The two men were seen in a security video standing in front of the prime suspect as he removed a backpack and placed it on a bench at the crowded shrine shortly before the blast, and police had believed they were accomplices.