Thailand's junta said Thursday 15 suspects in last week's bomb and arson attacks against a string of tourist resort towns are being detained at a military barracks in Bangkok.
"Authorities have detained 17 suspects at the special 11th Army Circle barracks in Bangkok but we had released two of them," Colonel Burin Tongprapai, the junta's top legal advisor, told reporters.
Colonel Burin said authorities were looking to re-detain the two suspects who were released and that the entire group were likely to be charged on Friday.
No one has claimed responsibility for the bombing spree, which hit tourist towns in the country's south last Thursday and Friday, killing four and wounding dozens, including European visitors.
The attacks were highly unusual in a country where foreign visitors are rarely caught up in the country's frequent bouts of political violence.
Colonel Burin's comments highlight the primary role the military have played in the investigation and is the first official admission that scores of suspects have been held since the bombings on army barracks.
Local human rights groups had previously said more than a dozen suspects were being held without access to lawyers and called for greater transparency in the investigation.
Authorities have remained tight-lipped on the motive of the attackers or the identities of anyone detained.
Thailand's junta, which seized power in 2014, and the police quickly ruled out international terrorism, saying the perpetrators were "local saboteurs".