The opening months of Colorado’s recreational marijuana industry have seen a rise in fiery explosions as pot users try to extract potent oil from the drug at home laboratories. Hospital officials say more people are being seriously burned and injured trying to make hash oil. The golden concoction can be up to 80 percent THC, marijuana’s intoxicating chemical. Devotees say one or two drops can produce a more euphoric high than a joint. But home cooking is dangerous. Authorities who track explosions in Colorado say there have been at least 31 since legal sales started in January, up from 11 last year. The state’s only certified adult burn center has treated 10 people for second and third-degree burns.