The investigation into the killing the schoolboy Robert Holohan in Co Cork is understood to be focusing on a small number of suspects in the belief that he may have been killed during a row by someone he knew.
The post-mortem examination yesterday revealed no evidence of sexual assault and detectives are understood to feel it is less likely that he was abducted and murdered by a sex offender.
The post-mortem, carried out by the State Pathologist, Dr Marie Cassidy, confirmed that Robert died from asphyxiation.
Although gardaí did not elaborate, it is understood that he choked from being caught in an arm lock.
They are believed to be examining the possibility that Robert may have got into a row with some person he knew and that this disagreement resulted in him being choked, after which the killer panicked and brought the body to a spot close to Inch Strand.
The theory that he knew his assailant is supported by the absence of any evidence of a struggle at the scene where his bicycle was found at Carrigoghna, 500 yards from his home at Ballyedmond outside Midleton.
It is understood the post-mortem revealed other injuries which may support the theory that Robert was physically assaulted, but gardaí believe he was not killed where his body was found.