The court has agreed to issue one additional arrest warrant in relation to the explosions outside Siam Paragon department store in downtown Bangkok last Sunday.
Police had initially applied for two warrants, but the court only approved one yesterday.
Meanwhile, police said the investigation is 70 per cent complete and witness accounts have been helpful, though details cannot yet be revealed. Police also said they could neither confirm nor deny if those involved in the bombs were from Bangkok or not.
Police said that while the first two primary suspects had been captured on CCTV, they have discovered that at least another two people might have been involved in the bomb plot as well.
Police said the court refused to issue an arrest warrant for one of the two suspects yesterday because more evidence was needed to justify an arrest warrant, adding that police will try to furnish the court with more proof.
New security measures are being introduced in key spots from today onwards to prevent a recurrence of the incident.
Asked if one of the suspects was a former ranger, police said they were investigating the matter. Reporters learned that the new suspects are believed to be the same two who were arrested for transporting home-made bombs in January last year at Bangkok's Soi Phaholyothin 52.