An explosion inside the Phramongkutklao Hospital that left 24 injured was likely to come from a bomb.
Deputy commissioner of the Royal Thai Police Pol Gen Srivara Ransibrahmanakul said an object that was similar to an integrated circuit was found by explosive ordnance disposal police indicating it might be an explosion from small explosive.
The explosive had a narrow destructive range of a few metres, he said.
However the EOD team is still scouring the room for more evidence.
Earlier at noon today the director of the hospital held a brief press conference to reveal the number of injuries caused by the explosion at the dispensing room on the first floor of the Chalermphrakiat Building inside the hospital compound.
The room dispenses medications to retired and sick army officers.
The hospital director did not give details of the explosion.
But earlier it was said to be the explosion of a power transformer, and later of an oxygen tank.
But the arrival of more EOD police and soldiers and the sealing of the area with no entry signs casts speculation of a bomb explosion.
Government spokesman Lt Gen Sansern Kaewkamnerd also did not say exactly the cause of the explosion at a press briefing late today.