Thai police are now hunting for four people besides the man they arrested last Saturday in connection with the deadly Aug 17 rush-hour blast in downtown Bangkok that claimed 20 lives.
Among the four was a woman identified as Wanna Suansant, said to be 26, who had rented the flat where police over the weekend found bomb-related materials such as urea-based fertiliser, bolts, decorative lights as well as a radio operated toy. A warrant of arrest has also been issued for an unidentified foreign man.
Both Ms Wanna - the first name to emerge from the investigation - and the man are said to have used the flat. A picture of Ms Wanna, whose Muslim name is reportedly Misaloh, was released as well as an artist's impression of the unidentified man.
An earlier warrant was issued for another unidentified man in a yellow shirt, also believed to be a foreigner, who was caught on closed-circuit television (CCTV) cameras apparently planting the bomb at the Erawan Shrine.
The fourth warrant of arrest was for an unidentified man caught on CCTV pushing a heavy object in a bag into a canal at Sathon pier, several kilometres from the shrine. The object exploded in the water the next day, but nobody was hurt.
Police said that it was the same type of bomb as the one in the Erawan attack.
A team of police and soldiers searched Ms Wanna's family home on the island of Phang Nga yesterday afternoon but she was not there.
Her relatives reportedly cooperated and said they had not seen her for three months.
The police, who succeeded in contacting her, said she was apparently in Turkey, and had told them she was innocent and would fly back to Thailand to cooperate.
Meanwhile, the man detained last Saturday with an array of bomb-making materials and several dozen apparently fake Turkish passports in the rented flat, who was initially uncooperative, has apparently begun to yield information, police said. However, no details have emerged on his identity.
Police said they are working with "several embassies" to try to ascertain his identity.
The authorities have not concluded or ruled out any possible motive for the attack, National Council for Peace and Order spokesman Winthai Suvaree said on television after a meeting of the council.
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