Police spokesman Prawut Thavornsiri said authorities were seeking an arrest warrant for a 10th suspect, who was a foreigner but declined to reveal his nationality, the Bangkok Post reported.
A sketch of the new suspect was completed, he said.
Prawut suggested the suspect was deeply involved in the network that is believed to have carried out the August 17 bombing at the popular Erawan Brahma temple during rush-hour, and another one the next day near a busy river pier that caused no casualties as the bomb exploded in the water.
Arrest warrants have been issued for seven other suspects in the case and the police seems to have made considerable progress in their probe into the bombing that killed 20 people and injured over 100 others since the raid on an apartment in Bangkok's outskirts on August 29.
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They arrested a man named on a fake Turkish passport as Adem Karadag in possession of bomb-making materials, the first such detention in the case after nearly two weeks of struggle in a breakthrough.
The 28-year-old, whose nationality has still not been confirmed, was later taken to the Min Buri prison in eastern Bangkok. A suspect can be detained for up to seven 12-day periods, or 84 days in total, before formal charges must be laid.
Police tested the man's DNA against samples taken from a taxi, a banknote and shreds of a backpack recovered at the shrine, all of which were believed to come from the man who planted the bomb. Though they were not a match, authorities believe the suspect had a role in the bombing plot.
Yusufu's fingerprints, however, matched those collected from a container of explosive materials found at the apartment and from a nail clipper found in a rented room at the apartment building in Min Buri.
The Post report also cited another report in the Matichon Online as saying that Yusufu, a chemical engineer from a well- known university in China, might have assembled the bomb.
It said that the yellow-shirted man, who acted in a team with him, placed the bomb while Yusufu was believed to have detonated it from the skywalk.