When detectives did finally launch a major probe in tamaulipas , they found that a cell of the deadly zetas gang was organizing oil robbery and transporting the crude into texas .
Detectives in laredo say he quickly became affiliated with a local gang known as los chachos , one of four groups that controlled the city 's drug trade in those days .
From the moment joanna yeates 's body was found , detectives emphasised how important scientific work would be in establishing how she had died and convicting her murderer .