Police said they were also holding one suspect in custody, however, they declined to give any information for fear of harming the investigation.
Deputy Bangkok police chief Pol Maj-General Parinya Chansuriya said yesterday investigators were following leads relating to four to five suspects after looking at CCTV footage. They were also checking licence plates of a Toyota Fortuna and Isuzu pick-up truck parked in the area.
Police had not ruled out any motive for the bomb, but based on new evidence, investigators were now suspected the motive may be linked to an adulterous affair.
Parinya dismissed as untrue rumours on social media that there was another bomb but noted that security had been beefed up in key areas of the capital as a precaution.
Metropolitan Police spokesman Maj-General Adul Narongsak said police had interviewed 19 witnesses and were holding one suspect but declined to elaborate.
National police chief Pol Gen Adul Saengsingkaew reiterated that the bombing was unlikely to be related to conflict in the deep South as the bomb used different components from those used by insurgents.