The reporter answered that Santa Teresa was a center of the drug trade and most likely nothing happened there that wasn't related to the phenomenon one way or the other.
And what exactly does that tell us? Not much. At page 463 we are told explicitly for the first time that Pedro Rengifo is a narcotraficante. We certainly suspected this at the time that Lalo commenced his employment as a bodyguard for Rengifo's wife, but we were not told. Still, Rengifo is not a particularly malevolent character. We have a sense that he is simply a businessman in a dangerous business.
The narcotics traffic does not get a lot of play in the novel. It is simply something that is there in the background. In that regard it is worthwhile to remember that the situation in the Mexican border states in 1993-95 was a different situation by several magnitudes than it is today after Felipe Calderon started the war with the drug lords with the support of the United States as he promised in his 2006 campaign.
The sentence quoted at the outset is the only indication anywhere in the novel—that I recall—that suggests even a tenuous connection between the narcotics traffic and the murders.