INVESTIGATORS believe that the plotters behind the Erawan Shrine and Sathorn pier blasts might have relied on a foreign bomb-making technique, an informed source said.
"Such a technique did not exist in Thailand before. And our in-depth investigations reveal that foreigners of unknown nationality came to Thailand in 2011 to provide training on such a technique," the source said.
The suspected bomber wanted in connection with the bloody attack at the Erawan Shrine does not look Thai.
The shrine attack occurred on Monday night and the bloodless pier attack happened on Tuesday afternoon. The shrine blast killed 20 people and injured more than 100. The bomb at the pier exploded in a canal.
According to the source, TNT was used for both pipe bombs.
"Explosive powder was stuffed into steel pipes with a huge number of ball bearings," the source added.
The source said the detonation of a TNT bomb could be delayed for several days, if an electric circuit was involved. "This means the authorities will have to go back at least four days when examining security footage." The source said the pier bomber clearly did not intend to cause any casualties as the bomb was placed in a canal directly adjacent to the Chao Phraya River.
"That person must have known full well that the destructive power of the bomb would be reduced when it is immersed in water," the source said.
Police have also considered the possibility that the pier blast might have been unintentional, as the person who discarded the bomb in the water might have just wanted to get rid of the explosives after the attack at the shrine, the source said.
Security footage showed the person, who put the bag believed to contain a bomb in the canal, did so not long after the shrine attack.
Another source disclosed that the suspected shrine bomber took a taxi to the Hua Lamphong train station and then took a tuk-tuk to the shrine on Monday.
"Police are trying to locate the taxi driver. We have been informed that the taxi picked up the suspect from Yannawa area," the source added.
The tuk-tuk driver gave police the Bt20 (S$0.79) the suspect used to pay the fare.
"The bank note has been submitted to the scientific crime detection unit for fingerprint and DNA analysis. It could provide crucial evidence to nail down the suspect," the source added. Police spokesman Lt-General Prawut Thavornsiri said a sketch of the suspect had been given to Interpol so that 190 other countries could help with the search for the suspect.
He confirmed that there had been much progress in the case. "But I can't disclose details."
The National Council for Peace and Order shared his stance.
"Officials are working to bring the culprits to justice. But at this point, we can't disclose details, as that may affect the ongoing investigations," NCPO spokesman Winthai Suvari said yesterday in a nationally televised statement.
He said 56 of the shrine-blast victims remained hospitalised.
In a related development, officials from the Chinese embassy in Bangkok accompanied the relatives of four Chinese tourists killed at the shrine to the Institute of Forensic Medicine yesterday.
The relatives secured the bodies ahead of the funeral rites being held.
See also: More stories on the Bangkok bombing