Gangs from nearby Jalisco and Michoacán moved into the state from 2015. They are not led by El Chapo-style narcos. They make most of their money from theft and extortion. Some of the loot, including grain, car parts and furniture, is hijacked from trains bound for the United States. The biggest money-maker is fuel theft. Nearly a fifth of recorded cases occur in Guanajuato. The country-wide cost of this to Pemex, the state-controlled oil firm, is more than 30bn pesos ($1.6bn) a year.
Huachicoleros, as the thieves are called, fight each other and oil-industry workers for control of pipelines, just as drug gangs war over highways, border crossings and street corners. A politician in Guanajuato claims that 80% of murders in the state are related to fuel theft.
Here is more from The Economist. Of course this is disquieting because Gunajuato has even quite recently been one of the safer parts of Mexico.