The unidentified foreigner, who is being held in military custody at an undisclosed location, was seized during a yesterday morning raid on a flat on the eastern outskirts of Bangkok. Investigators say he was found with bomb-making equipment and multiple passports.

The interrogation is not making progress because the suspect is not really giving useful information," army chief General Udomdej Sitabutr said. "We have to conduct further interrogations and make him better understand so he will be more cooperative - while we have to be careful not to violate the suspect's rights," he added.

The blast that hit the Erawan shrine in a busy Bangkok shopping district on August 17 was Thailand's worst single mass-casualty attack, killing 20 people - most of them ethnic Chinese tourists from across Asia. Police and the junta have been keen to play down any suggestion the attack was launched by international terrorists or specifically targeted Chinese tourists.

National police spokesman Prawut Thavornsiri said officers believed the suspect was part of a people-smuggling gang who helped illegal migrants obtain counterfeit documents -- and that the bomb attack was retaliation for a recent crackdown by Thai authorities.

"They (the gang) are unsatisfied with police arresting illegal entrants," he told Channel 3 in a telephone interview without elaborating how investigators knew this.

Bangkok has long had a reputation for crime groups that produce counterfeit documents, while Thailand has been a major regional hub for both people-smuggling and people-trafficking. Pictures released by police on Saturday showed stacks of Turkish passports which were allegedly found at the suspect's flat. Police said they believe the passports are fake.

Authorities have yet to say what nationality the man is. Prawut told reporters outside police headquarters that investigators were working "with several embassies" to ascertain his identity as well as using multiple translators.

Asked which languages, he confirmed English but would not be drawn on the others. Defence Minister Prawit Wongsuwan also told AFP the suspect is known to speak some English. Other members of the gang are now being sought while DNA samples are being taken from the suspect, police spokesman Prawut added.

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