The police probing Thailand's worst attack at a Brahma temple issued arrest warrants against two more suspects, including a woman, after they seized bomb- making materials from an apartment here, widening their hunt for the people involved in the assault.

One arrest warrant was for a woman named Wanna Suansant, 26, who rented a room in Bangkok's Min Buri district, Police spokesman Prawut Thawornsiri said.

Wanna is the first suspect to be identified in the investigation into the August 17 bombing at Erawan Shrine as well as another blast the next day that caused no injuries.

The sketches of the two suspects -- a male and a woman in a head scarf -- were released in a nationwide live telecast. Min Buri is near the district where an unidentified foreigner was arrested on Saturday, allegedly in possession of bomb-making paraphernalia including detonators and ball- bearings as well as dozens of fake passports.

The arrested man was carrying a fake Turkish passport but his identity remained unclear as Turkish diplomats said they did not believe he was a Turk.

During the raid at Wanna's room yesterday, police found urea-based fertiliser, a radio-controlled toy vehicle, components of which could be used to detonate a bomb remotely, bolts that could be used as shrapnel and decorative lights that could be used for ignition.

Items seized from the woman's apartment room were shown on the televised police briefing. The second arrest warrant was for an unidentified man of unknown nationality.

Prawut cautioned owners of apartments frequented by foreigners to keep a close watch on them and report anyone of similar appearance or who was found behaving in a suspicious manner. The two new arrest warrants raised to four the number of people now wanted for involvement in the bombing that killed 20 people and injured 131.

The motive behind the attack is still not clear.

Photograph: Courtesy Thai police