Investigators are blaming an Ohio nursing home fire — which killed one person and hospitalized five others — on a methamphetamine lab in a resident’s room.

The 31-year-old man who was killed in the blaze, which broke out Sunday night, was not a resident of the facility, according to local reports. Police said they expect to file criminal charges against two other men who sustained burns in the fire, the Associated Press reported. Neither of these men were residents. Investigators are working to figure out how long the meth lab existed without being detected. Officials suspect that at least one resident knew of the lab’s existence.

Park Haven Home, a skilled nursing facility located in Ashtabula, OH, has a one-star rating from Medicare’s Nursing Home Compare’s website, and was cited for 18 violations from state surveyors in 2011. The facility also received low fire-safety marks according to Nursing Home Compare. State records show that the facility had 39 residents.

Ashtabula Fire Chief Ron Pristera told USA Today that this was the first meth lab fire he’s ever seen in a nursing home. Pristera described the meth operation as a “pop bottle, shake-and-bake lab.” These types of labs are increasingly leading to uninsured burn patients taxing hospitals, according to the Associated Press.

The Ohio Department of Health, which oversees the state’s nursing homes, is investigating the fire at Park Haven.