Thai police are hunting for further suspects linked to Bangkok’s worst-ever bomb attack after the arrest of a foreigner allegedly involved in the plot spawned more questions than answers.

Authorities said they were tracking hundreds of phone numbers and passports after detaining the suspect in a raid in Bangkok on Saturday, but they have yet to reveal his name, nationality or any information on motive or possible accomplices. A raid on Sunday on a second address yielded no evidence, police said.

The mystery has been intensified by officials’ continued insistence that the August 17 murder of 14 foreigners and six Thais at the Erawan shrine in the capital’s heart was no international conspiracy. Thai media reports have linked the detained man to a Turkish passport whose identity page was widely broadcast after the arrest, but the document is suspected to be a fake.