Thai police are questioning two men who were identified as suspects in Monday's bomb attack in central Bangkok.
The men - who were caught on closed-circuit television footage with the chief suspect shortly before the evening blast - had turned themselves in and insisted that they were tour guides, according to a BBC report.
Agence France-Presse reported late last night that a man had been questioned and freed.
Earlier in the day, the Thai authorities said international terrorists were "unlikely" to have been responsible for Monday's deadly blast as they asked Interpol to aid in investigations.
In a televised address by the junta yesterday, a presenter announced: "Security agencies have collaborated with intelligence agencies from allied countries and come to the same preliminary conclusion that the incident is unlikely to be linked to international terrorism."
She added that "Chinese tourists were not the direct target".
The denial was in response to speculation that the attack at Erawan Shrine, which killed 20 people and injured over 100, was a retaliation against Thailand's recent deportation of some Uighur migrants to China. That move was roundly criticised for putting the Muslim minority at risk of persecution.
Thai police have issued a sketch and obtained an arrest warrant for the bombing suspect, who was caught on CCTV leaving a backpack at the crowded shrine just before the blast. The fair, bearded and bespectacled man has a thick mob of hair and facial features which police had earlier thought to be European or Middle Eastern.
Yesterday, though, both Prime Minister Prayut Chan-o-cha and national police chief Somyot Pumpanmuang suggested instead that the man could have been disguised to look like a foreigner. "He could have been from inside the country," said Police General Somyot, adding that the attack had been planned in advance by a big network.
The preliminary conclusion caught some security analysts by surprise. International Crisis Group analyst Matthew Wheeler said: "I suspect that there is an international aspect to this, as the police chief suggested earlier. And there is some circumstantial evidence that points in this direction - including the targets, including many foreigners - and the design of the explosive device, which is not commonly seen in Thailand. It appears that the government has made a conscious decision to try to frame this attack as a domestic affair."
Since coming to power after a coup in May last year, the military government has been trying to keep the lid on a tinderbox of conflicts. The most high-profile involves the protracted struggle between the country's elites and the emerging middle class outside of Bangkok, many of whom are associated with the "red shirts" who support exiled premier Thaksin Shinawatra and his sister Yingluck Shinawatra. Ms Yingluck was ousted as premier last year, shortly before the military takeover. In southern Thailand, a separatist insurgency has claimed more than 6,000 lives over the past decade.
The bomb attack comes at a sensitive time, as the junta is trying to consolidate its position amid jockeying among various ruling factions and growing dissatisfaction with the faltering economy. General Prayut has replaced his entire economic team in a Cabinet reshuffle that was formalised yesterday.
The capital remains on alert, after someone hurled a second bomb off a bridge by the Chao Phraya River on Tuesday, a day after the Erawan Shrine blast. It detonated underwater without injuring anyone.
Workmen began repairing the Erawan Shrine yesterday while visitors returned to make offerings at the Brahma statue, which remains largely intact after the blast.