BANGKOK -- Thai explosives experts say substance from the bomb that blew up in downtown Bangkok last week smells like TNT, although police still have not received chemical test results, the national police spokesman said Wednesday.

Prawuth Thavornsiri told journalists that it was still not clear if the bomb that killed 20 people Aug. 17 was made of TNT or C4, a plastic explosive. But the bomb disposal experts believe it contained TNT based on the power of the blast and "the smell" left behind, he said.

Prawuth says investigators are trying to find other pieces of the bomb to analyze.

More than a week after the bombing at the Erawan Shrine, which also left 120 people injured, police appear to be no closer to tracking down suspects or determining a motive for the attack.

Police have released an artist's sketch of the suspect who was seen in a security camera video from the open-air shrine leaving a backpack at a bench and walking away. A separate camera showed the suspect, wearing a yellow T-shirt, on the back of a motorcycle taxi leaving the site.

But authorities say they don't know if the suspect has left the country, what his nationality is or if the attack was linked to internal affairs or international terrorism.