The authorities have said the group that carried out the bombing was involved in human trafficking, but until Wednesday, they had avoided connecting the case to the Uighurs. A directive issued by the Interior Ministry last week instructed officials not to refer to Uighurs when discussing the bombing, and to call the attack a “disturbance,” not terrorism.

Until Wednesday, the police had not disclosed the nationality of the man arrested on Tuesday or of an additional suspect, described only as a “foreign man,” who was arrested on Saturday with a counterfeit Turkish passport. That man’s nationality remains unknown.

The Turkish Embassy in Bangkok said on Wednesday that it had asked the Thai Foreign Ministry for information about the man arrested Saturday, and about stacks of Turkish passports, also possibly counterfeit, that were found in his apartment. In an emailed statement, the embassy said it was ”awaiting an official reply from the Thai authorities.”

A spokeswoman for the Chinese Ministry of Foreign Affairs said that the ministry had “noticed relevant media reports” and was in close contact with the Thai authorities. “The Chinese authorities will continuously pay close attention to the investigation of the case,” she added. “We believe that whoever committed this heinous crime must be severely punished by the law.”

Dilxat Raxit, spokesman of the World Uyghur Congress, an exile group, called the shrine explosion “a heartbreaking and condemnable event” and urged the Thai police to “present accurate and transparent evidence.”

The repatriation of Uighurs to China in July prompted heavy criticism of Thailand’s military government by human rights groups and by foreign governments, which said the Uighurs were likely to face persecution on their return. But if the bombing proves to be connected to the repatriation, the military government could be criticized for a different reason — that it had jeopardized the safety of the country.