The DSI's conclusion has come as no surprise. It fits widespread suspicion by locals and relatives of the dead boy that police in the province have been involved in numerous suspicious deaths.

Kiattisak Thitbunkhrong, 17, was originally said to have hung himself in a farm hut in Roi Et, a neighbouring province in July 2004 - a day after he was arrested by a team of Muang station officers for motorcycle theft.

DSI spokesman Piyawat Kingket did not identify the five officers allegedly involved in the death. He said the number could increase depending on whether evidence pointed to more officers being involved. All up, a total of 12 had to undergo a polygraph (lie-detector) test.

Piyawat said the autopsy report found that Kiattisak was killed eight hours before his body was hung at the hut. A DSI source said the boy was silenced possibly because he knew too much about gangs stealing motorcycles in the province.

Responding to complaints by people that more than 20 murders had occurred in Kalasin and nearby provinces from 2003 to 2005, Piyawat said the DSI could only look into matters it was assigned to.

Kiattisak's grandmother, known only as Sa, sent a complaint to His Majesty the King, which led to the DSI looking into the case. She said she believed in justice and repeated her long-held conviction that officers at Kalasin city police station had something to do with her grandson's death.