CLARKSVILLE, Tenn. -- The daughter of late country music singer June Carter Cash was found dead in a parked bus along with a Nashville bluegrass fiddle player, authorities said.

Officials said Saturday that carbon monoxide from six propane or kerosene heaters on the bus may have killed the two and that an autopsy was planned. The bodies were found Friday afternoon.

Ted Denny, spokesman for the Montgomery County Sheriff's Department, said Saturday that the deaths were "suspicious." He said emergency medical workers found drug paraphernalia, including needles and pipes, on the bus near the bodies.

Investigators identified the victims as Rosey Nix Adams, who also was the 45-year-old stepdaughter of late singing legend Johnny Cash; and Jimmy Campbell, 40, a bluegrass fiddle player who performed and recorded in Nashville for more than a decade.

Adams and her husband, Philip Adams, had recently sold a home in Montgomery County and were preparing to travel in the bus. The bus was parked behind the house for repairs.

Investigators said the bus may have been owned by the late bluegrass pioneer Bill Monroe.

Rosey Nix Adams' mother died in May, and Johnny Cash died last month.