Thai police said they arrested a foreigner on Saturday who matched the description of a man who left a bag at the site of a Bangkok blast that killed 20 people nearly two weeks ago.
Police raided a decaying four-storey apartment block in a suburb of the capital and found "multiple" fake passports and bomb-making materials they said may have been used in the Aug. 17 bombing at a Hindu shrine, the deadliest in the country's history.
The suspect was a 28-year-old foreign man who had been in Thailand since January last year. He was being held at a military facility on charges of possessing illegal explosives and had admitted the passports were fake, police said.
"It's unlikely to be terrorism," Police chief Somyot Pumpanmuang told a news conference. "It's not an international terrorist act," he said of the attack.
Somyot did not explain how police had come to that conclusion, but said the motive was "taking personal revenge for his comrades". He did not elaborate.
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The bomb tore through the crowded Erawan Shrine, one of the country's top tourist attractions and close to several of Bangkok's most luxurious hotels and biggest shopping malls.
Among the dead were 14 foreigners, seven from mainland China and Hong Kong, in an attack the military government said was intended as a strike at Thailand's ailing economy. Scores of people were wounded.
Police have found few clues to the mystery of who masterminded the devastating attack.