Two men identified as suspects in the Bangkok bombing have been cleared of involvement, police say.
A police spokesman said they were now satisfied the men - a Chinese tourist and his Thai guide - were not involved.
The main suspect remains at large, but authorities told the BBC they believe he is still in Thailand.
Dozens of people were injured in the explosion, with some losing limbs.
Police had said that at least 10 people were suspected of involvement in the attack, and that their prime target was foreign.
The two former suspects, wearing red and white t-shirts, were captured standing in front of the main suspect, in yellow, as he left his backpack under a bench at the scene.
The footage led police to believe the pair may have been the attacker's accomplices.
But one of the men "met police and was released", according to police spokesman Prawut Thavornsiri.
He told them he had taken the Chinese man to the Erawan shrine on behalf of a mutual friend.
Earlier reports suggested both of the men had presented themselves for questioning.
But the Chinese national returned home a day after the bomb, Mr Thavornsiri said.
Neither were "likely involved", he added.
Earlier on Thursday, Col Winthai Suvaree, a spokesman for the ruling military junta, said the preliminary conclusion was that it was "unlikely" the attack was the work of an international terror group.
However, he later told Associated Press that a global terrorism link had not been ruled out, saying: "We still have to investigate in more detail."
Images of the main suspect before and after the bombing give a chilling picture of a man on a deadly mission.
We see him getting out of a tuk-tuk 18 minutes before the blast, with a black backpack. He is no more than three minutes walk from the shrine, and starts towards it.
He appears again at 18.49.30, about 100m on from the previous CCTV camera. We then see him walking into the shrine, taking off the backpack, and putting it on the ground, under the bench he is sitting on.
He walks out. It is less than three minutes before the explosion.
The cameras then pick him up walking back along Rajdamri Road, past the Hyatt Hotel, looking at his phone.
The next camera catches him at 18.56.06, 48 seconds after the blast, walking fast.
We see him next on the back of a motorbike taxi, heading south, towards Lumpini Park, where the driver has told police he dropped him off. The police say they have lost all trace of him since then.
Police are also questioning a tuk-tuk taxi driver who drove the main suspect to the shrine, but are making slow progress in identifying the name and nationality of the man in yellow.
Although the shrine has been cleaned up, a BBC team led by Jonathan Head was still able to find bomb shrapnel embedded in a wall nearby, suggesting the forensic teams have not yet collected all possible evidence from the area.
No-one has yet said they carried out the attack.
National police chief Somyot Pumpanmuang said he believed the attack was planned at least a month in advance.
Prime Minister Prayuth Chan-ocha has called the bombing the "worst ever attack" on Thailand.
Twelve of the 20 dead in Monday's attack were foreigners, including nationals from China, Hong Kong, the UK, Indonesia, Malaysia and Singapore.