A notorious Kansas serial killer currently locked up in prison for 10 murders he committed is still a suspect in a decades-old disappearance in Oklahoma.

Osage County, Oklahoma, Sheriff Eddie Virden says BTK killer Dennis Rader remains a top suspect in the disappearance of Cynthia Kinney. The 16-year-old Kinney was last seen at the Osage Laundry in Pawhuska, Oklahoma, in 1976.

Virden says Kinney’s name and the name of the street where she was last seen appear in a wordsearch puzzle that Rader sent to the media 20 years ago.

Late last summer Virden indicated old pictures Dennis Rader took of himself could link the BTK killer to more cold cases in three different states, including Kansas.

Rader resides at the Eldorado Correction Facility, where he is serving a minimum of 175 years.