Ohio's Attorney General says marijuana grow operations were found at three of the four places where eight relatives were shot dead in "execution type" killings.
Authorities did not provide further details.
Drugs, violence, gangs and charred bodies are all part of day-to-day life in the treacherous Sinaloa region of Mexico - where two Australian surfers are believed to have gone missing.
Adam Coleman and Dean Lucas's burnt-out van was found in the Navolato section of the notorious state which has earned the dubious nickname of 'The Cemetery' due to the large amount of executed bodies thought to be dumped there.
It's a region where vast quantities of marijuana, cocaine and other illicit substances are thought to be widely available and violence and danger are rife with hundreds or murders taking place each year.
It is here the Sinaloa Cartel - an international drug trafficking, money laundering, and organised crime syndicate - is believed to operate.
The cartel is widely regarded as one of the most powerful drug trafficking organisations in the world, and Mexico's most powerful organised crime group.