Two men, who were seen on CCTV minutes before the Bangkok bomb blast, have handed themselves in and been cleared by Thai police, agencies said.
The pair had been considered suspects by authorities, were seen on the CCTV footage standing in front the main suspect ahead of the attack at Erawan Shrine Monday.
Police said Thursday one of the them turned out to be a Chinese tourist while the other is his Thai tour guide. They are no longer suspects.
Police believe the main suspect is still in Thailand.
Checks at airports and other exit points found that no one matching the description of the main suspect had left the country since the attack. Besides him, 10 others were involved.
“They include those who looked out on the streets, prepared the bomb and those at the site and … those who knew the escape route. I believe there must have been at least 10 people involved,” National police chief Somyot Pumpanmuang said.
The attack was planned at least a month in advance and international terrorists had no role in it.
With no breakthrough in the case yet, police have sought the help of Interpol.
Prime Minister Prayuth Chan-ocha said the man seen in the CCTV footage was in disguise.
The criminal altered his appearance, he said.
“It means there was preparation. It was as though he knew a camera was going to be there,” he said.
Earlier, he said the attack was Thailand’s problem and it should be resolved internally. On Thursday, he described it as a threat to South East Asia.
The blast comes at a sensitive time for Thailand, which has been riven for a decade by a sometimes-violent struggle for power between political factions in Bangkok.
A parliament hand-picked by a junta that seized power in a 2014 coup is due to vote on a draft constitution next month.
Critics say the draft is undemocratic and intended to help the army secure power and curb the influence of elected politicians. The government has promised to restore democracy late next year.
The Erawan shrine, which is popular with Buddhists and Hindus in Thailand, was reopened Wednesday.
Visitors have left messages of condolence, flowers and candles at the site.