The Bangkok bombing case is officially closed, Thail police announced Monday.

According to CNBC, Thai police announced that the two main suspects are in custody and have confessed to the August bombing, which killed 20 people and injured 125 at the Erawan shrine. Among those who were confirmed deceased were a Chinese national and a Filipino national.

Thai police interviewed more than 200 witnesses and reviewed footage from security cameras. They also found ball bearings at the shrine, as well as pieces of a damaged bag believed to have carried the bomb.

Police chief Somyot Pumpanmuang declared the case closed and stated, "The case is now concluded. Perpetrators are members of a human-smuggling network."

"However, we haven't ruled out the possibility that this group could have been hired by others. More investigation is needed," he later added.

Throughout the month-long investigation, 17 people were named suspects. Out of the 17 suspects, two were arrested.

Adem Karadag, who was accused of dumping a black backpack minutes before the explosion occurred while wearing a yellow T-shirt caught by security cameras, was declared an accomplice instead of the bomber.

Many people have serious doubts about the investigation being closed. Somyot, who is scheduled to retire next week, appeared before the media with $83,000 in banknotes. He claimed that the money was for his officers as a reward for all their hard work solving the case.

Thailand is known to have a huge human trafficking problem, and the government is cracking down hard on the problem. Reports state the motive for the bombing was revenge for the government's crackdown on human trafficking gangs.

There were no international terrorist groups involved in the bombing. The Ewaran shrine bombing is the captial's worst mass causality attack.

The shrine attracts thousands of people per year.