A home-made C4 bomb was likely to have been used in the attack on a police hoist parked at Rajdamnoen Nok Avenue on Friday night, according to Explosive Ordnance Disposal (EOD) officials.
The attack took place near the Police Museum and the Parus Gawan Palace.
EOD officials did not find a safety pin so they suspect the assailants used a home-made bomb, a C4-type weighing around 0.5 kg, which had an explosion radius of 20 metres and a destruction radius of five metres.
Six glass windows on the second floor of Chitralada Palace, located within the same fence with the Police Museum, shattered.
Pol Lt-Colonel Sitthisak Nakamat, deputy superintendent of Dusit Police Station, said initial investigations found that two men wearing crash helmets while riding motorcycles were responsible for the attack.
The suspects did not intend to kill or injure anyone but intended to cause public terror, police said.
The scene of the bomb attack was about 140 metres from the bunker put up to protect the Makkhawan Rangsan Bridge rally stage of the Students and People’s Network for Thailand’s Reform.