BANGKOK • Investigators believe that the plotters behind the two explosions that hit Bangkok last week might have relied on a foreign bomb-making technique, The Nation reported yesterday, citing an anonymous source.
The revelation came as Thai police yesterday said they were investigating new security camera footage showing a man dropping a package into a canal, where a device exploded last Tuesday without injuring anyone.
That second blast intensified anxiety in an already rattled city, following last Monday's bomb attack on a religious shrine in Bangkok that killed 20 people and wounded scores more.
"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.
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."
Closed-circuit television video widely circulated by the local media yesterday showed a man in a blue T-shirt kicking the package off a footbridge where the second blast occurred. The authorities have not ruled out a link between the two explosions. The shrine bomb killed mostly ethnic Chinese tourists from across Asia, and has left the police scrambling to find the assailants responsible.
National police spokesman Prawut Thavornsiri confirmed that the new footage was being examined to decide whether the man dropping the package into the water near Saphan Thaksin pier was a suspect. "We have to verify the information," he said, adding that the situation was "still confusing".
The unverified footage is time- stamped just a few minutes after last Monday's blast. It shows the man in the blue T-shirt carrying something heavy in a plastic bag. He goes to the side of a footbridge, places the bag down and then uses his cellphone.
About a minute later, he pushes the bag into the canal with his foot, kicking up a visible splash of water.
The following day, an explosion went off in the canal, which is near a popular tourist pier, sending people scurrying for cover.
Until now, the search for the perpetrator of last Monday's attack has focused on a primary suspect in a yellow T-shirt seen placing a heavy rucksack under a bench at the shrine.
Asked whether the man in the blue T-shirt and the one in the yellow T-shirt could be the same person, Lieutenant-General Prawut said: "It's likely the two men are different." Ousted Thai prime minister Thaksin Shinawatra's son said that he had more than doubled the reward offered by the police for the capture of the main suspect by putting up nearly US$200,000 (S$280,000).
AGENCE FRANCE-PRESSE, THE NATION/ASIA NEWS NETWORK