Adams, 45, was also the step-daughter of Johnny Cash, who died last month. 

Adams along with veteran fiddler Jimmy Campbell were reportedly discovered dead on the tour bus about 5:30 PM local time by Philip Adams, the husband of Rosey Nix Adams. 

The cause of death has not yet been determined. Authorities say that carbon monoxide poisoning may be the cause. The Tennessean reports that authorities also suspect that the bus was being used as a drug lab. 

Eric Reese of Montgomery County Emergency Medical Service, who was one of the emergency personnel first on the scene told a sheriff�s deputy that he suspected a possible �meth lab� on the bus. 

Some drug paraphernalia was found on the bus including needles and pipes. Authorities in early speculation point towards six propane or kerosene heaters found on the bus which may have led to carbon monoxide poisoning.  Such heaters can be used to manufacture or �cook� crystal methamphetamine. 

Police warn people not to jump to any conclusions at this point. ''We cannot pinpoint a cause, carbon monoxide poisoning or drug overdose,'' Ted Denny, Sheriff's Department spokesman, said yesterday. ''It's just pure speculation until the coroner's report.'' .