Gov. Rodrigo Medina says the images released by the newspaper Reforma are “overwhelming.”

He announced the investigation Wednesday along with proposals to prevent new casinos in the northern Mexico state and to better regulate existing ones.

Gunmen entered the Casino Royale in Monterrey on Thursday, spread gasoline and set the building on fire, trapping and asphyxiating dozens in what’s believed to be a case of extortion.

The five arrested so far confessed to being part of the Zetas drug cartel.