PAWHUSKA, Okla. (AP) — The defense attorney for the BTK serial killer insisted Tuesday that his client was not involved in the 1976 disappearance of an Oklahoma teenager, even as the dispute between the sheriff and prosecutor over the investigation intensified.

Defense attorney Rob Ridenour said in a statement disputing Dennis Rader’s involvement in Cynthia Kinney’s disappearance that his client has already confessed to his crimes. He said Rader was already interviewed by the sheriff’s department about Kinney, a cheerleader from the northern Oklahoma city of Pawhuska, who was last seen at a laundromat.

Rader, now 78, killed from 1974 to 1991, giving himself the nickname BTK — for “bind, torture and kill.” He played a cat and mouse game with investigators and reporters for decades before he was caught in 2005. He is serving 10 life terms in the neighboring state of Kansas, one for each of the victims he confessed to killing.

Ridenour released the statement one day after Osage County, Oklahoma, District Attorney Mike Fisher raised questions about how Sheriff Eddie Virden was handling the investigation.

Osage County sheriff’s officials, including Undersheriff Gary Upton, have recently called Rader a “prime suspect” in Kinney’s disappearance and the death of 22-year-old Shawna Beth Garber, whose body was discovered in December 1990 in McDonald County, Missouri.

In August, the sheriff’s office also released information from Rader’s journal entry in which he used the phrase “PJ-Bad Wash Day.” The entry said laundry mats were a “good place to watch victims and dream.”

A bank was installing new alarms across the street from the laundromat where Kinney was last seen, Virden has said. Rader was a regional installer for security system company ADT at the time, but Virden wasn’t able to confirm that Rader installed the bank’s systems.

But Fisher said he hadn’t seen anything “that at this point arises to the level of even reasonable suspicion” and called his relationship with the sheriff “broken.” He added that he asked the Oklahoma State Bureau of Investigation to open a formal investigation into Kinney’s disappearance because of the public interest in the revived cold case.

Virden said at a news conference Tuesday that he was “absolutely furious,” following up on a news release Monday in which his office accused Fisher of attempting to “derail the investigation” by contacting the prison where Rader was held in an attempt to halt further interviews.

The sheriff’s office said a task force has been created to help with the investigation.