Thai police on Thursday said they were looking at arrivals of Turkish nationals in the days before a Bangkok bomb attack that killed 20 people, but said they had not ruled out any group or possibility.
Police and some security analysts have raised the possibility of a connection to the Uighurs - a Turkic-speaking Muslim minority from the far west of China. They complain of persecution by Beijing.
China's treatment of the Uighurs is an important issue for many Turks, who see themselves as sharing a common cultural and religious background.
Last month more than 100 Uighurs were deported from Thailand to China - a move that prompted widespread condemnation by rights groups and sparked a protest outside Thailand's consulate in Istanbul.
National police spokesman Prawut Thavornsiri told reporters police had checked arrivals of Turkish nationals who entered Thailand around two weeks before the blast.
"There are probably more Turkish coming into Thailand than that. We investigated groups which may have come into the country," said Prawut, in response to whether police had investigated 15 Turkish nationals.
"We checked, but not 15 people," Prawut said, adding that police have not ruled out any group or nationality.
"We are not focused on the nationality but the individual," he said, without giving further details.
The main evidence police have for the blast at the Hindu Erawan Shrine popular with Asian tourists is security camera footage.
The footage shows a man with a yellow shirt and dark hair removing a backpack after entering the shrine and walking away from the scene before the explosion.
Twelve of the 20 dead in Monday's attack were foreigners, including nationals from China, Hong Kong, Britain, Indonesia, Malaysia and Singapore.
Anthony Davis, a Bangkok-based security analyst with IHS-Jane's, speaking at the Foreign Correspondent's Club of Thailand on Monday, said there were three "likely groupings" which have the motive and the capability to pull off the attack.
The most likely perpetrators of the bombing were militant members of a right-wing Turkish organization called the Grey Wolves, a pan-Turkic, extreme right-wing organization, he said.
Davis said their motive may have been revenge for Thailand's deportation of ethnic Uighurs to China.
"The Uighur cause is something they've latched onto in a big way," he said, adding that the Grey Wolves were "at the front of the queue" during an attack on the Thai consulate in Istanbul last month by a mob protesting Thailand's decision to extradite the Uighurs.