Gunpowder in a used cough syrup bottle, and not a ping pong ball, caused the blast at a Bangkok train station injuring two yesterday, Thai police confirmed.

Police revised their findings after further investigation into the Hua Lamphong explosion yesterday, the Bangkok Post reported.

Police said one of the injured men picked up the discarded cough syrup bottle and used it as an ashtray, igniting the gunpowder inside.

They believed the gunpowder remnants were placed in the bottle by a teenager or a technical school student, who left it behind.

A man was questioned over the incident, the daily reported.

Bombs ripped through central Bangkok last year, killing dozens.

Police blamed terrorists for the bombing at the capital's dense shopping district.