Synthetic marijuana is contributing to the two deadliest years in Florida prison history, with substances like K2 becoming the third most popular substance found in the system, The Miami Herald reports. The substance is now the top killer of inmates, according to an Florida Department of Corrections audit. The number of “accidental deaths” rose from 12 in 2016 to 67 in 2017—due mostly to the prevalence of K2 amongst inmates. The substance is popular in prisons where there is “absolutely nothing to do except get high,” former officer Keith Raimundo told the newspaper. Raimundo, who worked in Tomoka Correctional Institution Work Camp, told the newspaper he would often see inmates overdose while eating meals in the food hall, have seizures, and act like “zombies” because they were high. While K2 is preferred by inmates because it is not detectable in prison drug tests, it's often laced with “roach spray and rat poison.” While inmates can get addicted, there are few resources for them in prison to cope through withdrawals or get help. Raimundo also said that corrections officers and other prison staff would smuggle in the drugs and other contraband to sell to prisoners. The Florida report comes after K2 caused over 70 inmates to overdose in a two-hour span in New Haven, Connecticut earlier this month.